NAME

pl-examples - Perl One-Liner Examples

EXAMPLES

To steal ideas from one person is plagiarism. To steal from many is research. ;-)

Here's a wide variety of examples, many solving real-life problems. Often you can copy & paste them as-is. Or you need to make minor changes, e.g., to adapt them to your search expression. Many of these examples started out quite small, illustrating the power of pl. But to be generally useful, they're extended to cope with border cases. See canned commands for how you can make your favourite ones easier to use.

Only some of these are original. Many are adaptations from the various Perl one-liner web pages (Tom Christiansen, Peteris Krumins, CatOnMat, joyrexus, Richard Socher, eduonix, Geoff Broadwell (Windows syntax), Oracle, PerlMonks, perloneliner, Sundeep Agarwal: part 1, part 2 & cookbook) or videos (Walt Mankowski, Techalicious, David Oswald). This is no attempt to appropriate ownership, just to show how things are even easier and more concise with pl.

Dealing with Files

Heads ...

People say the back of my head looks really nice -- but I don't see it. :-)

If you want just n, e.g., 10, lines from the head of each file, use the optional number argument to -p, along with -r to reset the count. The program can be empty but must be present if you provide additional args:

pl -rp10 '' file*

If you want the head up to a regexp, use the flip-flop operator, starting with line number 1. Use the print-if-true -P loop option, again with -r to reset the count:

pl -rP '1../last/' file*

You can combine the two if you want at most n lines, e.g., 10:

pl -rP10 '1../last/' file*

... or Tails?

What has a head, a tail, but no legs? A penny. :-)

If you want a bigger number of last lines, you need to stuff them in a list; not worth it. But, if you want just 1 last line from each file, the end-of-file -e code (no need to quote, as it has no special characters) can E(cho) it for you, capitalized to not add another newline (yes, Perl is case sensitive):

pl -e Echo '' file*
pl -e E '' file*

If you want the tail from a line-number (e.g., 99) or a regexp, use the flip-flop operator, starting with your regexp and going till each end-of-file:

pl -P '99..eof' file*
pl -P '/first/..eof' file*

You can even get head and tail (which in programming logic translates to print if in 1st or 2nd range) if last line of head comes before 1st line of tail (or actually any number of such disjoint ranges):

pl -rP '1../last/ or /first/..eof' file*

Remove Trailing Whitespace in Each File

This print-loops (-p) over each file, replacing it (-i) with the modified output. Line ends get stripped on reading and added on printing (-l) because they're also whitespace (\s). At each end of line, substitute one or more spaces of any kind (incl. DOS newlines) with nothing:

pl -pli 's/\s+$//' file*

Tabify/Untabify Each File

This print-loops (-p) over each file, replacing it (-i) with the modified output. At beginning of line and after each tab, this converts 8 spaces or less than 8 followed by a tab to a tab:

pl -pi '1 while s/(?:^|\t)\K(?: {1,7}\t| {8})/\t/' file*

To go the other way, subtract the tab-preceding length modulo 8, to get the number of spaces to replace with:

pl -pi '1 while s/^([^\t\n]*)\K\t/" " x (8 - length($1) % 8)/e' file*

Fans of half-width tabs make that:

pl -pi '1 while s/(?:^|\t)\K(?: {1,3}\t| {4})/\t/' file*
pl -pi '1 while s/^([^\t\n]*)\K\t/" " x (4 - length($1) % 4)/e' file*

Print Only 1st Occurrence of Each Line

Poets create worlds through a minimal of words. -- Kim Hilliker |/|

This counts repetitions of lines in a hash. Print only when the expression is true (-P), i.e., the count was 0:

pl -P '!$a{$_}++' file*

If you want this per file, you must empty the hash in the end-of-file -e code:

pl -Pe '%a = ()' '!$a{$_}++' file*

Remove Empty Lines

Or, actually the opposite, printing back to the same files (-Pi) all lines containing non-whitespace \S:

pl -Pi '/\S/' file*

Move a Line Further Down in Each File

Assume we have lines matching "from" followed by lines matching "to". The former shall move after the latter. This loops over each file, replacing it with the modified output. The flip-flop operator becomes true when matching the 1st regexp. Capture something in there to easily recognize it's the first, keep the line in a variable and empty $_. When $1 is again true, it must be the last matching line. Append the keep variable to it.

pl -pi 'if( /(f)rom/.../(t)o/ ) {
        if( $1 eq "f" ) { $k = $_; $_ = "" } elsif( $1 ) { $_ .= $k }
    }' file*

Rename a File Depending on Contents

This reads each file in an -n loop. When it finds the package declaration, which gives the logical name of this file, it replaces double colons with slashes. It renames the file to the result. The last statement then makes this the last line read of the current file, continuing with the next file:

pl -n 'if( s/^\s*package\s+([^\s;]+).*/$1/s ) {
        s!::!/!g;
        rename $ARGV, "$_.pm" or warn "$ARGV -> $_.pm: $!\n";
        last;
    }' *.pm
pl -n 'if( s/^\s*package\s+([^\s;]+).*/$1/s ) {
        s!::!/!g;
        rename $A, "$_.pm" or warn "$A -> $_.pm: $!\n";
        last;
    }' *.pm

This assumes all files are at the root of the destination directories. If not, you must add the common part of the target directories before $_.

On Windows this won't quite work because that locks the file while reading. There you must add close ARGV; (or close A;) before the rename.

For Java it's a bit more complicated because the full name is split into a package followed by a class or similar statement. Join them when we find the latter:

pl -n 'if( /^\s*package\s+([^\s;]+)/ ) {
        $d = $1 =~ tr+.+/+r;
    } elsif( /^\s*(?:(?:public|private|protected|abstract|sealed|final)\s+)*(?:class|interface|enum|record)\s+([^\s;]+)/ ) {
        rename $ARGV, "$d/$1.java" or warn "$ARGV -> $d/$1.java: $!\n";
        last;
    }' *.java
pl -n 'if( /^\s*package\s+([^\s;]+)/ ) {
        $d = $1 =~ tr+.+/+r;
    } elsif( /^\s*(?:(?:public|private|protected|abstract|sealed|final)\s+)*(?:class|interface|enum|record)\s+([^\s;]+)/ ) {
        rename $A, "$d/$1.java" or warn "$A -> $d/$1.java: $!\n";
        last;
    }' *.java

Delete Matching Files, Except Last One

If you have many files, which sort chronologically by name, and you want to keep only the last one, it can be quite painful to formulate Shell patterns. Check on each iteration of the -o loop, whether the index $ARGIND (or $I) is less than the last, before unlinking (deleting). If you want to test it first, replace unlink with e(cho):

pl -o 'unlink if $ARGIND < $#ARGV' file*
pl -o 'unlink if $I < $#A' file*

If your resulting list is too long for the Shell, let Perl do it. Beware that the Shell has a clever ordering of files, while Perl does it purely lexically! The -A code assigns the result to @A(RGV), as though it came from the command line. This list is then popped (shortened) in -B begin code, instead of checking each time. Since the programs don't contain special characters, you don't even need to quote them:

pl -oA '<file*>' -B pop unlink

You can exclude files by any other criterion as well:

pl -oA 'grep !/keep-me/, <file*>' unlink

File Statistics

42% of statistics are made up! :-)

Count Files per Suffix

Find and pl both use the -0 option to allow funny filenames, including newlines. Sum up encountered suffixes in sort-numerically-at-end hash %N(UMBER):

find -type f -print0 |
    pl -0ln 'm@[^/.](\.[^/.]*)?$@;
        ++$NUMBER{$1 // "none"}'
find -type f -print0 |
    pl -0ln 'm@[^/.](\.[^/.]*)?$@;
        ++$N{$1 // "none"}'

>          4: .3
>          4: .SHs
>          4: .act
>         ...
>         88: .json
>        108: .tml
>        136: .xml
>        224: .yml
>        332: .xs
>        376: .sh
>        412: .ucm
>        444: .PL
>        512: .c
>        640: .h
>        696: .txt
>        950: .pod
>       1392: .pl
>       2988: none
>       3264: .pm
>      10846: .t

Count Files per Directory per Suffix

There are three types of people: those who can count and those who can't. (-:

Match to first or last / and from last dot following something, i.e., not just a dot-file. Store sub-hashes in sort-by-key-and-stringify-at-end hash %R(ESULT). Count in a nested hash of directory & suffix:

find -type f -print0 |
    pl -0ln 'm@^(?:\./)?(.+?)/.*?[^/.](\.[^/.]*)?$@;
        ++$RESULT{$1}{$2 // "none"}'
find -type f -print0 |
    pl -0ln 'm@^(?:\./)?(.+?)/.*?[^/.](\.[^/.]*)?$@;
        ++$R{$1}{$2 // "none"}'

>   perl-5.30.0:  {
>     '.1' => 3,
>     '.3' => 1,
>     '.PL' => 111,
>     ...
>     '.yml' => 56,
>     none => 747
>   }
>   ...
>   perl-5.30.3:  {
>     '.1' => 3,
>     '.3' => 1,
>     '.PL' => 111,
>     '.SH' => 9,
>     ...'
>     '.perl' => 1,
>     '.perldb' => 2,
>     '.ph' => 1,
>     '.pht' => 1,
>     '.pkg' => 1,
>     '.pl' => 348,
>     '.yml' => 56,
>     none => 747
>   }

find -type f -print0 |
    pl -0ln 'm@^(?:\./)?(.+)/.*?[^/.](\.[^/.]*)?$@;
        ++$RESULT{$1}{$2 // "none"}'
find -type f -print0 |
    pl -0ln 'm@^(?:\./)?(.+)/.*?[^/.](\.[^/.]*)?$@;
        ++$R{$1}{$2 // "none"}'

>   perl-5.30.3:  {
>     '.SH' => 8,
>     '.act' => 1,
>     ...
>     '.yml' => 3,
>     none => 15
>   }
>   perl-5.30.3/Cross:  {
>     '.new' => 1,
>     '.patch' => 2,
>     '.sh-arm-linux' => 1,
>     '.sh-arm-linux-n770' => 1,
>     none => 9
>   }
>   ...
>   perl-5.30.3/lib:  {
>     '.pl' => 5,
>     '.pm' => 36,
>     '.pod' => 2,
>     '.t' => 41
>   }
>   perl-5.30.3/lib/B:  {
>     '.pm' => 2,
>     '.t' => 3
>   }
>   perl-5.30.3/lib/Class:  {
>     '.pm' => 1,
>     '.t' => 1
>   }
>   perl-5.30.3/lib/Config:  {
>     '.pm' => 1,
>     '.t' => 1
>   }
>   ...
>   perl-5.30.3/t:  {
>     '.pl' => 4,
>     '.supp' => 1,
>     none => 3
>   }
>   perl-5.30.3/t/base:  {
>     '.t' => 9
>   }
>   perl-5.30.3/t/benchmark:  {
>     '.t' => 1
>   }
>   ...

This is the same pivoted, grouping by suffix and counting per directory:

find -type f -print0 |
    pl -0ln 'm@^(?:\./)?(.+)/.*?[^/.](\.[^/.]*)?$@;
        ++$RESULT{$2 // "none"}{$1}'
find -type f -print0 |
    pl -0ln 'm@^(?:\./)?(.+)/.*?[^/.](\.[^/.]*)?$@;
        ++$R{$2 // "none"}{$1}'

>   ...
>   .pl:  {
>     'perl-5.30.3' => 8,
>     ...
>     'perl-5.30.3/dist/Attribute-Handlers/demo' => 11,
>     'perl-5.30.3/dist/Devel-PPPort/devel' => 3,
>     'perl-5.30.3/dist/Devel-PPPort/parts' => 2,
>     'perl-5.30.3/dist/Devel-PPPort/t' => 1,
>     'perl-5.30.3/dist/IO/hints' => 1,
>     'perl-5.30.3/dist/Storable/hints' => 4,
>     ...
>   }
>   ...
>   .pm:  {
>     'perl-5.30.3' => 1,
>     'perl-5.30.3/Porting' => 2,
>     ...
>     'perl-5.30.3/dist/Attribute-Handlers/lib/Attribute' => 1,
>     'perl-5.30.3/dist/Carp/lib' => 1,
>     'perl-5.30.3/dist/Carp/lib/Carp' => 1,
>     'perl-5.30.3/dist/Data-Dumper' => 1,
>     'perl-5.30.3/dist/Data-Dumper/t/lib' => 1,
>     ...
>   }
>   ...
>   .pod:  {
>     'perl-5.30.3/Porting' => 8,
>     'perl-5.30.3/cpan/CPAN-Meta/lib/CPAN/Meta/History' => 5,
>     'perl-5.30.3/cpan/CPAN/lib/CPAN/API' => 1,
>     ...
>     'perl-5.30.3/dist/ExtUtils-ParseXS/lib' => 3,
>     'perl-5.30.3/dist/ExtUtils-ParseXS/lib/ExtUtils' => 1,
>     'perl-5.30.3/dist/Locale-Maketext/lib/Locale' => 1,
>     'perl-5.30.3/dist/Locale-Maketext/lib/Locale/Maketext' => 2,
>     ...
>   }
>   ...

This is similar but stores in sort-by-number-at-end %N(UMBER). Therefore, it sorts by frequency, only secondarily by directory & suffix (pl sorts stably):

find -type f -print0 |
    pl -0ln 'm@^(?:\./)?(.+)/.*?[^/.](\.[^/.]*)?$@;
        ++$NUMBER{"$1 " . ($2 // "none")}'
find -type f -print0 |
    pl -0ln 'm@^(?:\./)?(.+)/.*?[^/.](\.[^/.]*)?$@;
        ++$N{"$1 " . ($2 // "none")}'

>          1: perl-5.30.3 .act
>          1: perl-5.30.3 .aix
>          1: perl-5.30.3 .amiga
>          1: perl-5.30.3 .android
>          1: perl-5.30.3 .bs2000
>          ...
>          2: perl-5.30.3/Porting .c
>          2: perl-5.30.3/Porting .pm
>          ...
>        138: perl-5.30.3/cpan/Unicode-Collate/t .t
>        149: perl-5.30.3/pod .pod
>        206: perl-5.30.3/t/op .t

The function N(umber) can trim %N(UMBER), to those entries at least the argument (default 2):

find -type f -print0 |
    pl -0lnE Number 'm@^(?:\./)?(.+)/.*?[^/.](\.[^/.]*)?$@;
        ++$NUMBER{"$1 " . ($2 // "none")}'
find -type f -print0 |
    pl -0lnE N 'm@^(?:\./)?(.+)/.*?[^/.](\.[^/.]*)?$@;
        ++$N{"$1 " . ($2 // "none")}'

find -type f -print0 |
    pl -0lnE 'Number 80' 'm@^(?:\./)?(.+)/.*?[^/.](\.[^/.]*)?$@;
        ++$NUMBER{"$1 " . ($2 // "none")}'
find -type f -print0 |
    pl -0lnE 'N 80' 'm@^(?:\./)?(.+)/.*?[^/.](\.[^/.]*)?$@;
        ++$N{"$1 " . ($2 // "none")}'

>         82: perl-5.30.3/cpan/Math-BigInt/t .t
>         82: perl-5.30.3/hints .sh
>         84: perl-5.30.3/cpan/IO-Compress/t .t
>         87: perl-5.30.3/cpan/Unicode-Collate/Collate/Locale .pl
>        103: perl-5.30.3/cpan/Encode/ucm .ucm
>        117: perl-5.30.3/ext/XS-APItest/t .t
>        137: perl-5.30.3/dist/Devel-PPPort/parts/base none
>        137: perl-5.30.3/dist/Devel-PPPort/parts/todo none
>        138: perl-5.30.3/cpan/Unicode-Collate/t .t
>        149: perl-5.30.3/pod .pod
>        206: perl-5.30.3/t/op .t

Sum up File-sizes per Suffix

This illustrates a simpler approach: rather than the complicated regexps above, let Perl split each filename for us. Find separates output with a dot and -F splits on that. The \\ is to escape one backslash from the Shell. No matter how many dots the filename contains, 1st element is the size and last is the suffix. Sum it in %N(UMBER), which gets sorted numerically at the end:

find -type f -printf "%s.%f\0" |
    pl -0lF\\. '$NUMBER{@FIELD > 2 ? ".$FIELD[-1]" : "none"} += $FIELD[0]'
find -type f -printf "%s.%f\0" |
    pl -0lF\\. '$N{@FIELD > 2 ? ".$FIELD[-1]" : "none"} += $FIELD[0]'

>          0: .configure
>         16: .perldb
>         85: .xsh
>         90: .inf
>        118: .pmc
>        138: .plugin
>   ...
>    7167163: .c
>    7638677: .pod
>    7794749: .h
>    9742749: .ucm
>   11124074: .t
>   11617824: .pm
>   12259742: .txt

Count Files per Date

I feel more like I do now than I did a while ago. (-:

Incredibly, find has no ready-made ISO date, so specify the 3 parts. If you don't want days, just leave out -%Td. Sum up encountered dates in sort-value-numerically-at-end hash %N(UMBER):

find -type f -printf "%TY-%Tm-%Td\n" |
    pl -ln '++$NUMBER{$_}'
find -type f -printf "%TY-%Tm-%Td\n" |
    pl -ln '++$N{$_}'

>          1: 2018-07-19
>          1: 2019-04-10
>          ...
>         34: 2020-02-11
>         93: 2020-02-29
>       2816: 2018-06-27
>       3307: 2019-05-11
>       6024: 2019-10-21
>      12159: 2019-10-24

Count Files per Date with Rollup

Learn sign language! It's very handy. :-)

Rollup means, additionally to the previous case, sum up dates with the same prefix. The trick here is to count both for the actual year, month, and day, as well as replacing once only the day, once also the month with "__", and once also the year with "____". This sorts after numbers and gives a sum for all with the same leading numbers. Use the sort-by-key-and-stringify-at-end hash %R(ESULT):

find -type f -printf "%TY-%Tm-%Td\n" |
    pl -ln 'do { ++$RESULT{$_} }
        while s/[0-9]+(?=[-_]*$)/"_" x length $&/e'
find -type f -printf "%TY-%Tm-%Td\n" |
    pl -ln 'do { ++$R{$_} }
        while s/[0-9]+(?=[-_]*$)/"_" x length $&/e'

>   2018-06-27:  2816
>   2018-06-__:  2816
>   2018-07-19:  1
>   2018-07-__:  1
>   2018-__-__:  2817
>   2019-04-10:  1
>   2019-04-__:  1
>   ...
>   2019-11-10:  11
>   2019-11-25:  6
>   2019-11-__:  17
>   2019-12-05:  4
>   2019-12-__:  4
>   2019-__-__:  21581
>   ...
>   2020-05-14:  33
>   2020-05-15:  1
>   2020-05-17:  5
>   2020-05-29:  4
>   2020-05-__:  43
>   2020-__-__:  206
>   ____-__-__:  24604

Diff Several Inputs by a Unique Key

Always remember you're unique, just like everyone else. :-)

The function k(eydiff) stores the 2nd arg or chomped $_ in %K(EYDIFF) keyed by 1st arg or $1 and the arg counter $ARGIND (or $I). Its sibling K(eydiff) does the same using 1st arg or 0 as an index into @F(IELD) for the 1st part of the key. At the end these show only the rows differing between files. If you write to a terminal or specify --color the difference gets color-highlighted in per-character detail with Algorithm::Diff, or in just one red blob without. Here are examples for how to alias these as canned commands.

Diff Several CSV, TSV, or passwd Files by 1st Field

This assumes commaless key fields and no newline in any field. Else you need a CSV-parser package. -F implies -a, which implies -n (even using older than Perl 5.20, which introduced this idea). -F, splits each line on commas, and K(eydiff) by default takes the 1st field as your unique key:

pl -F, Keydiff *.csv
pl -F, K *.csv

>   1
>   	1,H,Hydrogen,1:H & alkali metal,1.008
>   	n/a
>   	1,H,Hydrogen,1:alkali metal,1
>   4
>   	4,Be,Beryllium,2:alkaline earth metal,9.012
>   	4,Pl,Perlium,2:pl basis,5.32.0
>   	n/a
>   8
>   	8,O,Oxygen,16:O & chalcogen,16
>   	8,O,Oxygen,16:O & chalcogen,16
>   	8,O,Oxygen,16:O and chalcogen,16
>   41
>   	41,Nb,Niobium,5:no name,92.906
>   	n/a
>   	41,Nb,Columbium,5:no name,93
>   42
>   	42,Ve,Veritasium,6:an element of truth,i
>   	n/a
>   	n/a
>   74
>   	74,W,Tungsten,6:transition metal,183.84
>   	74,W,Wolfram,6:transition metal,183.8
>   	n/a
>   80
>   	80,Hg,Mercury,12:no name,200.592
>   	80,Hg,Quicksilver,12:no name,200.6
>   	80,Hg,Hydrargyrum,12:no name,201
>   110
>   	n/a
>   	110,Ds,Darmstadtium,10:transition metal,[281]
>   	110,Ds,Darmstadtium,10:transition metal,281

This is similar but removes the key from the stored value, so it doesn't get repeated for each file. Note how k(eydiff) by default uses $1 as a key for $_. Additionally, in a -B begin program, show the filenames one per line:

pl -nB 'echo for @ARGV' 'keydiff if s/(.+?),//' *.csv
pl -nB 'e for @A' 'k if s/(.+?),//' *.csv

>   atom-weight-1.csv
>   atom-weight-2.csv
>   atom-weight-3.csv
>   1
>   	H,Hydrogen,1:H & alkali metal,1.008
>   	n/a
>   	H,Hydrogen,1:alkali metal,1
>   4
>   	Be,Beryllium,2:alkaline earth metal,9.012
>   	Pl,Perlium,2:pl basis,5.32.0
>   	n/a
>   8
>   	O,Oxygen,16:O & chalcogen,16
>   	O,Oxygen,16:O & chalcogen,16
>   	O,Oxygen,16:O and chalcogen,16
>   41
>   	Nb,Niobium,5:no name,92.906
>   	n/a
>   	Nb,Columbium,5:no name,93
>   42
>   	Ve,Veritasium,6:an element of truth,i
>   	n/a
>   	n/a
>   74
>   	W,Tungsten,6:transition metal,183.84
>   	W,Wolfram,6:transition metal,183.8
>   	n/a
>   80
>   	Hg,Mercury,12:no name,200.592
>   	Hg,Quicksilver,12:no name,200.6
>   	Hg,Hydrargyrum,12:no name,201
>   110
>   	n/a
>   	Ds,Darmstadtium,10:transition metal,[281]
>   	Ds,Darmstadtium,10:transition metal,281

A variant of CSV is TSV, with tab as separator. Tab is \t, which you must escape from the Shell as \\t, either with or without repeated keys:

pl -F\\t Keydiff *.tsv
pl -F\\t K *.tsv

>   1
>   	1	H	Hydrogen	1:H & alkali metal	1.008
>   	n/a
>   	1	H	Hydrogen	1:alkali metal	1
>   4
>   	4	Be	Beryllium	2:alkaline earth metal	9.012
>   	4	Pl	Perlium	2:pl basis	5.32.0
>   	n/a
>   8
>   	8	O	Oxygen	16:O & chalcogen	16
>   	8	O	Oxygen	16:O & chalcogen	16
>   	8	O	Oxygen	16:O and chalcogen	16
>   41
>   	41	Nb	Niobium	5:no name	92.906
>   	n/a
>   	41	Nb	Columbium	5:no name	93
>   42
>   	42	Ve	Veritasium	6:an element of truth	i
>   	n/a
>   	n/a
>   74
>   	74	W	Tungsten	6:transition metal	183.84
>   	74	W	Wolfram	6:transition metal	183.8
>   	n/a
>   80
>   	80	Hg	Mercury	12:no name	200.592
>   	80	Hg	Quicksilver	12:no name	200.6
>   	80	Hg	Hydrargyrum	12:no name	201
>   110
>   	n/a
>   	110	Ds	Darmstadtium	10:transition metal	[281]
>   	110	Ds	Darmstadtium	10:transition metal	281

pl -n 'keydiff if s/(.+?)\t//' *.tsv
pl -n 'k if s/(.+?)\t//' *.tsv

>   1
>   	H	Hydrogen	1:H & alkali metal	1.008
>   	n/a
>   	H	Hydrogen	1:alkali metal	1
>   4
>   	Be	Beryllium	2:alkaline earth metal	9.012
>   	Pl	Perlium	2:pl basis	5.32.0
>   	n/a
>   8
>   	O	Oxygen	16:O & chalcogen	16
>   	O	Oxygen	16:O & chalcogen	16
>   	O	Oxygen	16:O and chalcogen	16
>   41
>   	Nb	Niobium	5:no name	92.906
>   	n/a
>   	Nb	Columbium	5:no name	93
>   42
>   	Ve	Veritasium	6:an element of truth	i
>   	n/a
>   	n/a
>   74
>   	W	Tungsten	6:transition metal	183.84
>   	W	Wolfram	6:transition metal	183.8
>   	n/a
>   80
>   	Hg	Mercury	12:no name	200.592
>   	Hg	Quicksilver	12:no name	200.6
>   	Hg	Hydrargyrum	12:no name	201
>   110
>   	n/a
>   	Ds	Darmstadtium	10:transition metal	[281]
>   	Ds	Darmstadtium	10:transition metal	281

The same, with a colon as separator, if you want to compare passwd files from several hosts. Here we additionally need to ignore commented out lines:

pl -F: 'Keydiff unless /^#/' /etc/passwd passwd*
pl -n 'keydiff if s/^([^#].*?)://' /etc/passwd passwd*
pl -F: 'K unless /^#/' /etc/passwd passwd*
pl -n 'k if s/^([^#].*?)://' /etc/passwd passwd*

Diff Several zip Archives by Member Name

Growing old you forget to zip up your fly. Later you forget to unzip your fly. 8-)

This uses the same mechanism as the CSV example. Additionally, through the p(iped) block, it reads the output of unzip -vql for each archive. That has an almost fixed format, except with extreme member sizes:

pl -oB 'echo for @ARGV' 'piped {
        keydiff if s@.{29,}% .{16} [\da-f]{8}\K  (.+)@@;
    } "unzip", "-vqq", $_' *.zip
pl -oB 'e for @A' 'p {
        k if s@.{29,}% .{16} [\da-f]{8}\K  (.+)@@;
    } "unzip", "-vqq", $_' *.zip

>   perl-5.30.0.zip
>   perl-5.30.1.zip
>   perl-5.30.2.zip
>   perl-5.30.3.zip
>   AUTHORS
>   	   48831  Defl:N    22282  54% 2019-05-11 11:50 cc2a1286
>   	   48864  Defl:N    22297  54% 2019-10-24 23:27 b793bcc5
>   	   48927  Defl:N    22338  54% 2020-02-29 12:55 8cecd35e
>   	   48927  Defl:N    22338  54% 2020-02-11 14:31 8cecd35e
>   Artistic
>   	    6321  Defl:N     2400  62% 2019-05-11 11:50 fa53ec29
>   	    6321  Defl:N     2400  62% 2019-10-24 22:17 fa53ec29
>   	    6321  Defl:N     2400  62% 2019-10-24 22:17 fa53ec29
>   	    6321  Defl:N     2400  62% 2019-10-21 13:20 fa53ec29
>   Changes
>   	    3168  Defl:N     1273  60% 2018-06-27 13:17 66a9af3e
>   	    3111  Defl:N     1246  60% 2019-10-27 10:52 f826c349
>   	    3111  Defl:N     1246  60% 2019-10-27 10:52 f826c349
>   	    3111  Defl:N     1246  60% 2019-10-28 09:05 f826c349
>   ...

Java .jar, .ear & .war files (which are aliases for .zip), after a clean build have many class files with the identical CRC but a different date. This excludes the date. Here are examples for how to combine these variants as Shell functions:

pl -o 'piped {
        keydiff $2 if s@.{16} ([\da-f]{8})  (.+)@$1@;
    } "unzip", "-vqq", $_' *.zip
pl -o 'p {
        k $2 if s@.{16} ([\da-f]{8})  (.+)@$1@;
    } "unzip", "-vqq", $_' *.zip

>   AUTHORS
>   	   48831  Defl:N    22282  54% cc2a1286
>   	   48864  Defl:N    22297  54% b793bcc5
>   	   48927  Defl:N    22338  54% 8cecd35e
>   	   48927  Defl:N    22338  54% 8cecd35e
>   Changes
>   	    3168  Defl:N     1273  60% 66a9af3e
>   	    3111  Defl:N     1246  60% f826c349
>   	    3111  Defl:N     1246  60% f826c349
>   	    3111  Defl:N     1246  60% f826c349
>   Configure
>   	  587687  Defl:N   148890  75% 144c0f25
>   	  587687  Defl:N   148890  75% 144c0f25
>   	  587825  Defl:N   148954  75% 6761d877
>   	  587825  Defl:N   148954  75% 6761d877
>   INSTALL
>   	  108059  Defl:N    37351  65% 45af5545
>   	  108085  Defl:N    37371  65% e5f2f22b
>   	  107649  Defl:N    37211  65% 9db83c1e
>   	  107649  Defl:N    37211  65% 16726160
>   ...

Browsers have a bug of not checking for updated CSS & JavaScript. A common workaround is to add a hex number to those file names. In that case use only the meaningful part of the filename as a key:

pl -o 'piped {
        keydiff $2
            if s@.{16} ([\da-f]{8})  (.+?)(?:\.([0-9a-f]{20})(\..[a-z]+))?$@if( $3 ) {
                $n = "$2.\$x$4"; "$1  \$x=$3"
            } else {
                $n = $2; $1
            }@e
    } "unzip", "-vqq", $_' *.jar
pl -o 'p {
        k $2
            if s@.{16} ([\da-f]{8})  (.+?)(?:\.([0-9a-f]{20})(\..[a-z]+))?$@if( $3 ) {
                $n = "$2.\$x$4"; "$1  \$x=$3"
            } else {
                $n = $2; $1
            }@e
    } "unzip", "-vqq", $_' *.jar

Diff Several Tarballs by Member Name

Actually I'm very different. But I rarely find time for it. -- von Horváth :-)

This is like the zip example. Alas, tar gives no checksums, so this is less reliable. Exclude directories, by taking only lines not starting with a d. Each time pl sees a wider owner/group or file size, columns shift right. Reformat the columns, to not show this as a difference:

pl -oB 'echo for @ARGV' 'piped {
        keydiff $4
            if s!^[^d]\S+ \K(.+?) +(\d+) (.{16}) (.+)!Form "%-20s %10d %s", $1, $2, $3!e;
    } "tar", "-tvf", $_' *.tar *.tgz *.txz
pl -oB 'e for @A' 'p {
        k $4
            if s!^[^d]\S+ \K(.+?) +(\d+) (.{16}) (.+)!F "%-20s %10d %s", $1, $2, $3!e;
    } "tar", "-tvf", $_' *.tar *.tgz *.txz

>   perl-5.30.0.txz
>   perl-5.30.1.txz
>   perl-5.30.2.txz
>   perl-5.30.3.txz
>   ...
>   cpan/Compress-Raw-Bzip2/bzip2-src/decompress.c
>   	-r--r--r-- pfeiffer/pfeiffer         20948 2018-06-27 13:17
>   	-r--r--r-- pfeiffer/pfeiffer         20948 2019-10-24 22:17
>   	-r--r--r-- pfeiffer/pfeiffer         21287 2020-02-29 12:55
>   	-r--r--r-- pfeiffer/pfeiffer         21287 2020-02-12 18:41
>   cpan/Compress-Raw-Bzip2/bzip2-src/huffman.c
>   	-r--r--r-- pfeiffer/pfeiffer          6991 2018-06-27 13:17
>   	-r--r--r-- pfeiffer/pfeiffer          6991 2019-10-24 22:17
>   	-r--r--r-- pfeiffer/pfeiffer          6986 2020-02-29 12:55
>   	-r--r--r-- pfeiffer/pfeiffer          6986 2020-02-12 18:41
>   cpan/Compress-Raw-Bzip2/bzip2-src/randtable.c
>   	-r--r--r-- pfeiffer/pfeiffer          3866 2018-06-27 13:17
>   	-r--r--r-- pfeiffer/pfeiffer          3866 2019-10-24 22:17
>   	-r--r--r-- pfeiffer/pfeiffer          3861 2020-02-29 12:55
>   	-r--r--r-- pfeiffer/pfeiffer          3861 2020-02-12 18:41
>   cpan/Compress-Raw-Bzip2/fallback/constants.h
>   	-r--r--r-- pfeiffer/pfeiffer          7238 2018-06-27 13:17
>   	-r--r--r-- pfeiffer/pfeiffer          7238 2019-10-24 22:17
>   	-r--r--r-- pfeiffer/pfeiffer          7238 2019-10-24 22:17
>   	-r--r--r-- pfeiffer/pfeiffer          7238 2019-10-21 13:20
>   ...

Same without the date:

pl -o 'piped {
        keydiff $3
            if s!^[^d]\S+ \K(.+?) +(\d+) .{16} (.+)!Form "%-20s %10d", $1, $2!e;
    } "tar", "-tvf", $_' *.tar *.tgz *.txz
pl -o 'p {
        k $3
            if s!^[^d]\S+ \K(.+?) +(\d+) .{16} (.+)!F "%-20s %10d", $1, $2!e;
    } "tar", "-tvf", $_' *.tar *.tgz *.txz

>   ...
>   cpan/Compress-Raw-Bzip2/bzip2-src/decompress.c
>   	-r--r--r-- pfeiffer/pfeiffer         20948
>   	-r--r--r-- pfeiffer/pfeiffer         20948
>   	-r--r--r-- pfeiffer/pfeiffer         21287
>   	-r--r--r-- pfeiffer/pfeiffer         21287
>   cpan/Compress-Raw-Bzip2/bzip2-src/huffman.c
>   	-r--r--r-- pfeiffer/pfeiffer          6991
>   	-r--r--r-- pfeiffer/pfeiffer          6991
>   	-r--r--r-- pfeiffer/pfeiffer          6986
>   	-r--r--r-- pfeiffer/pfeiffer          6986
>   cpan/Compress-Raw-Bzip2/bzip2-src/randtable.c
>   	-r--r--r-- pfeiffer/pfeiffer          3866
>   	-r--r--r-- pfeiffer/pfeiffer          3866
>   	-r--r--r-- pfeiffer/pfeiffer          3861
>   	-r--r--r-- pfeiffer/pfeiffer          3861
>   cpan/Compress-Raw-Bzip2/lib/Compress/Raw/Bzip2.pm
>   	-r--r--r-- pfeiffer/pfeiffer         10783
>   	-r--r--r-- pfeiffer/pfeiffer         10783
>   	-r--r--r-- pfeiffer/pfeiffer         11009
>   	-r--r--r-- pfeiffer/pfeiffer         11009
>   ...

Tarballs from the internet have a top directory of name-version/, which across versions would make every member have a different key. Exclude the 1st path element from the key by matching [^/]+/ before the last paren group:

pl -o 'piped {
        keydiff $4
            if s!^[^d]\S+ \K(.+?) +(\d+) (.{16}) [^/]+/(.+)!Form "%-20s %10d %s", $1, $2, $3!e;
    } "tar", "-tvf", $_' *.tar *.tgz *.txz
pl -o 'p {
        k $4
            if s!^[^d]\S+ \K(.+?) +(\d+) (.{16}) [^/]+/(.+)!F "%-20s %10d %s", $1, $2, $3!e;
    } "tar", "-tvf", $_' *.tar *.tgz *.txz

>   .dir-locals.el
>   	-r--r--r-- sawyer/sawyer               208 2018-06-27 13:17
>   	-r--r--r-- Steve/None                  208 2019-10-24 22:17
>   	-r--r--r-- Steve/None                  208 2019-10-24 22:17
>   	-r--r--r-- Steve/None                  208 2019-10-21 13:20
>   .lgtm.yml
>   	-r--r--r-- sawyer/sawyer               347 2019-05-11 11:50
>   	-r--r--r-- Steve/None                  347 2019-10-24 22:17
>   	-r--r--r-- Steve/None                  347 2019-10-24 22:17
>   	-r--r--r-- Steve/None                  347 2019-10-21 13:20
>   .metaconf-exclusions.txt
>   	-r--r--r-- sawyer/sawyer              1317 2019-05-11 11:50
>   	-r--r--r-- Steve/None                 1317 2019-10-24 22:17
>   	-r--r--r-- Steve/None                 1317 2019-10-24 22:17
>   	-r--r--r-- Steve/None                 1317 2019-10-21 13:20
>   .travis.yml
>   	-r--r--r-- sawyer/sawyer              2203 2019-05-11 11:50
>   	-r--r--r-- Steve/None                 2203 2019-10-24 23:27
>   	-r--r--r-- Steve/None                 2203 2019-10-24 23:27
>   	-r--r--r-- Steve/None                 2203 2019-10-21 13:20
>   AUTHORS
>   	-r--r--r-- sawyer/sawyer             48831 2019-05-11 11:50
>   	-r--r--r-- Steve/None                48864 2019-10-24 23:27
>   	-r--r--r-- Steve/None                48927 2020-02-29 12:55
>   	-r--r--r-- Steve/None                48927 2020-02-11 14:31
>   Artistic
>   	-r--r--r-- sawyer/sawyer              6321 2019-05-11 11:50
>   	-r--r--r-- Steve/None                 6321 2019-10-24 22:17
>   	-r--r--r-- Steve/None                 6321 2019-10-24 22:17
>   	-r--r--r-- Steve/None                 6321 2019-10-21 13:20
>   Changes
>   	-r--r--r-- sawyer/sawyer              3168 2018-06-27 13:17
>   	-r--r--r-- Steve/None                 3111 2019-10-27 10:52
>   	-r--r--r-- Steve/None                 3111 2019-10-27 10:52
>   	-r--r--r-- Steve/None                 3111 2019-10-28 09:05
>   ...

Again, without the date and owner/group, which can also vary:

pl -o 'piped {
       keydiff $2
            if s!^[^d]\S+ \K.+? +(\d+) .{16} [^/]+/(.+)!Form "%10d", $1!e;
    } "tar", "-tvf", $_' *.tar *.tgz *.txz
pl -o 'p {
       k $2
            if s!^[^d]\S+ \K.+? +(\d+) .{16} [^/]+/(.+)!F "%10d", $1!e;
    } "tar", "-tvf", $_' *.tar *.tgz *.txz

>   AUTHORS
>   	-r--r--r--      48831
>   	-r--r--r--      48864
>   	-r--r--r--      48927
>   	-r--r--r--      48927
>   Changes
>   	-r--r--r--       3168
>   	-r--r--r--       3111
>   	-r--r--r--       3111
>   	-r--r--r--       3111
>   Configure
>   	-r-xr-xr-x     587687
>   	-r-xr-xr-x     587687
>   	-r-xr-xr-x     587825
>   	-r-xr-xr-x     587825
>   ...

Diff ELF Executables by Loaded Dependencies

You get the idea: you can do this for any command that outputs records with a unique key. This one looks at the required libraries and which file they came from. For a change, loop with -O and $A(RGV) to avoid the previous examples' confusion between outer $_ which were the CLI args, and the inner one, which were the read lines:

pl -O 'piped {
       keydiff if s/^\t(.+\.so.*) => (.*) \(\w+\)/$2/;
    } ldd => $ARGV' exe1 exe2 lib*.so
pl -O 'p {
       k if s/^\t(.+\.so.*) => (.*) \(\w+\)/$2/;
    } ldd => $A' exe1 exe2 lib*.so

It's even more useful if you use just the basename as a key because version numbers may change:

pl -O 'piped {
       keydiff $2 if s/^\t((.+)\.so.* => .*) \(\w+\)/$1/;
    } ldd => $ARGV' exe1 exe2 lib*.so
pl -O 'p {
       k $2 if s/^\t((.+)\.so.* => .*) \(\w+\)/$1/;
    } ldd => $A' exe1 exe2 lib*.so

Looking at Perl

A pig looking at an electric socket: "Oh no, who put you into that wall?" :)

VERSION of a File

Print the first line (-P1) where the substitution was successful. To avoid the hassle of protecting them from (sometimes multiple levels of) Shell quoting, there are variables for single $q(uote) & double $Q(uote):

pl -P1 's/(?:\bpackage\s+[\w:]+\s+|.+\bVERSION\s*=\s*)[v$Quote$quote]{0,2}([0-9.]+).+/$1/' pl
pl -P1 's/(?:\bpackage\s+[\w:]+\s+|.+\bVERSION\s*=\s*)[v$Q$q]{0,2}([0-9.]+).+/$1/' pl

>   0.91.1

For multiple files, add the filename, and reset (-r) the -P count for each file:

pl -rP1 's/(?:\bpackage\s+[\w:]+\s+|.+\bVERSION\s*=\s*)[v$Quote$quote]{0,2}([0-9.]+).+/$ARGV: $1/' *.pm
pl -rP1 's/(?:\bpackage\s+[\w:]+\s+|.+\bVERSION\s*=\s*)[v$Q$q]{0,2}([0-9.]+).+/$A: $1/' *.pm

Only POD or non-POD

You can extract either parts of a Perl file, with these commands. Note that they don't take the empty line before into account. If you want that, and you're sure the files adhere strictly to this convention, use the option -00P instead (not exactly as desired, the empty line comes after things but still, before next thing). If you want only the 1st POD (e.g., NAME & SYNOPSIS) use the option -P1 or -00P1:

pl -P '/^=\w/../^=cut/' file*
pl -P 'not /^=\w/../^=cut/' file*

Count Perl Code

This makes __DATA__ or __END__ the last inspected line of (unlike in perl -n!) each file. It strips any comment (not quite reliably, also inside a string). Then it strips leading whitespace and adds the remaining length to print-at-end $R(ESULT):

pl -ln 'last if /^__(?:DATA|END)__/;
    s/(?:^|\s+)#.*//s;
    s/^\s+//;
    $RESULT += length' *.pm
pl -ln 'last if /^__(?:DATA|END)__/;
    s/(?:^|\s+)#.*//s;
    s/^\s+//;
    $R += length' *.pm

If you want the count per file, instead of $R(ESULT) use either sort-lexically $RESULT{$ARGV} (or $R{$A}) or sort-numerically $NUMBER{$ARGV} (or $N{$A}).

Content of a Package

Pl's e(cho) can print any item. Packages are funny hashes, with two colons at the end. Backslashing the variable passes it as a unit to Data::Dumper, which gets loaded on demand in this case. Otherwise, all elements would come out just separated by spaces:

pl 'echo \%List::Util::'
pl 'e \%List::Util::'

>   {
>     BEGIN => *List::Util::BEGIN,
>     EXPORT => *List::Util::EXPORT,
>     EXPORT_FAIL => *List::Util::EXPORT_FAIL,
>     EXPORT_OK => *List::Util::EXPORT_OK,
>     EXPORT_TAGS => *List::Util::EXPORT_TAGS,
>     ISA => *List::Util::ISA,
>     RAND => *List::Util::RAND,
>     REAL_MULTICALL => *List::Util::List::Util,
>     VERSION => *List::Util::VERSION,
>     XS_VERSION => *List::Util::XS_VERSION,
>     '_Pair::' => *{'List::Util::_Pair::'},
>     all => *List::Util::all,
>     any => *List::Util::any,
>     bootstrap => *List::Util::bootstrap,
>     first => *List::Util::first,
>     head => *List::Util::head,
>     import => *List::Util::import,
>     max => *List::Util::max,
>     maxstr => *List::Util::maxstr,
>     min => *List::Util::min,
>     minstr => *List::Util::minstr,
>     none => *List::Util::none,
>     notall => *List::Util::notall,
>     pairfirst => *List::Util::pairfirst,
>     pairgrep => *List::Util::pairgrep,
>     pairkeys => *List::Util::pairkeys,
>     pairmap => *List::Util::pairmap,
>     pairs => *List::Util::pairs,
>     pairvalues => *List::Util::pairvalues,
>     product => *List::Util::product,
>     reduce => *List::Util::reduce,
>     reductions => *List::Util::reductions,
>     sample => *List::Util::sample,
>     shuffle => *List::Util::shuffle,
>     sum => *List::Util::sum,
>     sum0 => *List::Util::sum0,
>     tail => *List::Util::tail,
>     uniq => *List::Util::uniq,
>     uniqint => *List::Util::uniqint,
>     uniqnum => *List::Util::uniqnum,
>     uniqstr => *List::Util::uniqstr,
>     unpairs => *List::Util::unpairs
>   }

Library Loading

Where does perl load from, and what exactly has it loaded?

pl 'echo \@INC, \%INC'
pl 'e \@INC, \%INC'

>   [
>     '/usr/share/perl/5.32',
>     '/etc/perl',
>     '/usr/local/lib/x86_64-linux-gnu/perl/5.32.1',
>     '/usr/local/share/perl/5.32.1',
>     '/usr/lib/x86_64-linux-gnu/perl5/5.32',
>     '/usr/share/perl5',
>     '/usr/lib/x86_64-linux-gnu/perl-base',
>     '/usr/lib/x86_64-linux-gnu/perl/5.32',
>     '/usr/share/perl/5.32',
>     '/usr/local/lib/site_perl'
>   ] {
>     'Carp.pm' => '/usr/share/perl/5.32/Carp.pm',
>     'Data/Dumper.pm' => '/usr/lib/x86_64-linux-gnu/perl/5.32/Data/Dumper.pm',
>     'Exporter.pm' => '/usr/share/perl/5.32/Exporter.pm',
>     'Exporter/Heavy.pm' => '/usr/share/perl/5.32/Exporter/Heavy.pm',
>     'List/Util.pm' => '/usr/lib/x86_64-linux-gnu/perl-base/List/Util.pm',
>     'XSLoader.pm' => '/usr/share/perl/5.32/XSLoader.pm',
>     'bytes.pm' => '/usr/share/perl/5.32/bytes.pm',
>     'constant.pm' => '/usr/share/perl/5.32/constant.pm',
>     'feature.pm' => '/usr/share/perl/5.32/feature.pm',
>     'overloading.pm' => '/usr/share/perl/5.32/overloading.pm',
>     'sort.pm' => '/usr/share/perl/5.32/sort.pm',
>     'strict.pm' => '/usr/share/perl/5.32/strict.pm',
>     'warnings.pm' => '/usr/share/perl/5.32/warnings.pm',
>     'warnings/register.pm' => '/usr/share/perl/5.32/warnings/register.pm'
>   }

Same, for a different Perl version, e.g., if you have perl5.28.1 in your path. This time copy %INC before calling e(cho), which for an array or hashref needs to load Data::Dumper on the fly and thus its dependencies:

pl -V5.28.1 '$orig = {%INC}; echo \@INC, $orig, \%INC'
pl -V5.28.1 '$orig = {%INC}; e \@INC, $orig, \%INC'

>   [
>     '/usr/share/perl/5.32',
>     '/etc/perl',
>     '/usr/local/lib/x86_64-linux-gnu/perl/5.28.1',
>     '/usr/local/share/perl/5.28.1',
>     '/usr/lib/x86_64-linux-gnu/perl5/5.28',
>     '/usr/share/perl5',
>     '/usr/lib/x86_64-linux-gnu/perl/5.28',
>     '/usr/share/perl/5.28',
>     '/usr/local/lib/site_perl',
>     '/usr/lib/x86_64-linux-gnu/perl-base'
>   ] {
>     'Exporter.pm' => '/usr/share/perl/5.32/Exporter.pm',
>     'Exporter/Heavy.pm' => '/usr/share/perl/5.32/Exporter/Heavy.pm',
>     'List/Util.pm' => '/usr/lib/x86_64-linux-gnu/perl/5.28/List/Util.pm',
>     'XSLoader.pm' => '/usr/share/perl/5.32/XSLoader.pm',
>     'feature.pm' => '/usr/share/perl/5.32/feature.pm',
>     'sort.pm' => '/usr/share/perl/5.32/sort.pm',
>     'strict.pm' => '/usr/share/perl/5.32/strict.pm',
>     'warnings.pm' => '/usr/share/perl/5.32/warnings.pm'
>   } {
>     'Carp.pm' => '/usr/share/perl/5.32/Carp.pm',
>     'Data/Dumper.pm' => '/usr/lib/x86_64-linux-gnu/perl/5.28/Data/Dumper.pm',
>     'Exporter.pm' => '/usr/share/perl/5.32/Exporter.pm',
>     'Exporter/Heavy.pm' => '/usr/share/perl/5.32/Exporter/Heavy.pm',
>     'List/Util.pm' => '/usr/lib/x86_64-linux-gnu/perl/5.28/List/Util.pm',
>     'XSLoader.pm' => '/usr/share/perl/5.32/XSLoader.pm',
>     'bytes.pm' => '/usr/share/perl/5.32/bytes.pm',
>     'constant.pm' => '/usr/share/perl/5.32/constant.pm',
>     'feature.pm' => '/usr/share/perl/5.32/feature.pm',
>     'overloading.pm' => '/usr/share/perl/5.32/overloading.pm',
>     'sort.pm' => '/usr/share/perl/5.32/sort.pm',
>     'strict.pm' => '/usr/share/perl/5.32/strict.pm',
>     'warnings.pm' => '/usr/share/perl/5.32/warnings.pm',
>     'warnings/register.pm' => '/usr/share/perl/5.32/warnings/register.pm'
>   }

Configuration

You get %Config::Config loaded on demand and returned by C(onfig):

pl 'echo Config'
pl 'e C'

>   {
>     Author => '',
>     CONFIG => 'true',
>     Date => '',
>     Header => '',
>     Id => '',
>     Locker => '',
>     Log => '',
>     PATCHLEVEL => '30',
>     PERL_API_REVISION => '5',
>     PERL_API_SUBVERSION => '0',
>     PERL_API_VERSION => '30',
>     ...
>   }

It returns a hash reference, from which you can look up an entry:

pl 'echo Config->{sitelib}'
pl 'e C->{sitelib}'

>   /usr/local/share/perl/5.32.1

You can also return a sub-hash, of only the keys matching any regexps you pass:

pl 'echo Config "random", qr/stream/'
pl 'e C "random", qr/stream/'

>   {
>     d_random_r => 'define',
>     d_srandom_r => 'define',
>     d_stdio_stream_array => undef,
>     random_r_proto => 'REENTRANT_PROTO_I_St',
>     srandom_r_proto => 'REENTRANT_PROTO_I_TS',
>     stdio_stream_array => ''
>   }

Tables

Number Bases

Perl natively handles the 4 different bases common to programming. If you want to list them side by side, quadruple them and f(orm) them with the 4 corresponding formats. Note the alternate parameter index syntax "1:":

pl 'form "0b%08b  0%1:03o  %1:3d  0x%1:02x"
        for 0..0xff'
pl 'f "0b%08b  0%1:03o  %1:3d  0x%1:02x"
        for 0..0xff'

>   0b00000000  0000    0  0x00
>   0b00000001  0001    1  0x01
>   0b00000010  0002    2  0x02
>   0b00000011  0003    3  0x03
>   0b00000100  0004    4  0x04
>   0b00000101  0005    5  0x05
>   0b00000110  0006    6  0x06
>   0b00000111  0007    7  0x07
>   0b00001000  0010    8  0x08
>   ...
>   0b11111100  0374  252  0xfc
>   0b11111101  0375  253  0xfd
>   0b11111110  0376  254  0xfe
>   0b11111111  0377  255  0xff

That makes a rather long table. You can get a better overview with 4 nested tables, looping over a preset @A(RGV):

pl -OA '0..0x3f' 'say join "\t",
    map Form( "0b%08b  0%1:03o  %1:3d  0x%1:02x", $ARGV+$_ ), 0, 0x40, 0x80, 0xc0'
pl -OA '0..0x3f' 'say join "\t",
    map F( "0b%08b  0%1:03o  %1:3d  0x%1:02x", $A+$_ ), 0, 0x40, 0x80, 0xc0'

>   0b00000000  0000    0  0x00	0b01000000  0100   64  0x40	0b10000000  0200  128  0x80	0b11000000  0300  192  0xc0
>   0b00000001  0001    1  0x01	0b01000001  0101   65  0x41	0b10000001  0201  129  0x81	0b11000001  0301  193  0xc1
>   0b00000010  0002    2  0x02	0b01000010  0102   66  0x42	0b10000010  0202  130  0x82	0b11000010  0302  194  0xc2
>   0b00000011  0003    3  0x03	0b01000011  0103   67  0x43	0b10000011  0203  131  0x83	0b11000011  0303  195  0xc3
>   0b00000100  0004    4  0x04	0b01000100  0104   68  0x44	0b10000100  0204  132  0x84	0b11000100  0304  196  0xc4
>   ...
>   0b00111101  0075   61  0x3d	0b01111101  0175  125  0x7d	0b10111101  0275  189  0xbd	0b11111101  0375  253  0xfd
>   0b00111110  0076   62  0x3e	0b01111110  0176  126  0x7e	0b10111110  0276  190  0xbe	0b11111110  0376  254  0xfe
>   0b00111111  0077   63  0x3f	0b01111111  0177  127  0x7f	0b10111111  0277  191  0xbf	0b11111111  0377  255  0xff

If you prefer to enumerate sideways, it's easier. @A(RGV) is in the right order so we can loop in chunks of 4:

pl -O4 -A '0..0xff' 'form join( "\t", map "0b%08b  0%$_:03o  %$_:3d  0x%$_:02x", 1..4 ), @$ARGV'
pl -O4 -A '0..0xff' 'f join( "\t", map "0b%08b  0%$_:03o  %$_:3d  0x%$_:02x", 1..4 ), @$A'

>   0b00000000  0000    0  0x00	0b00000001  0001    1  0x01	0b00000010  0002    2  0x02	0b00000011  0003    3  0x03
>   0b00000100  0004    4  0x04	0b00000101  0005    5  0x05	0b00000110  0006    6  0x06	0b00000111  0007    7  0x07
>   0b00001000  0010    8  0x08	0b00001001  0011    9  0x09	0b00001010  0012   10  0x0a	0b00001011  0013   11  0x0b
>   ...
>   0b11111000  0370  248  0xf8	0b11111001  0371  249  0xf9	0b11111010  0372  250  0xfa	0b11111011  0373  251  0xfb
>   0b11111100  0374  252  0xfc	0b11111101  0375  253  0xfd	0b11111110  0376  254  0xfe	0b11111111  0377  255  0xff

Inflation

Inflation is rearing its head. Here's the relative value of 1000 euros, dollars, ... after n years, with 1-20% inflation:

pl -MList::MoreUtils=pairwise '@a = (1000) x (@b = map 1 - $_ / 100, 1..20);
    form "  " . ("  " . (" %3d%%" x 5)) x 4, 1..20;
    form "%2d" . ("  " . (" %4d" x 5)) x 4, $_, pairwise { $a *= $b } @a, @b for 1..30'
pl -MList::MoreUtils=pairwise '@a = (1000) x (@b = map 1 - $_ / 100, 1..20);
    f "  " . ("  " . (" %3d%%" x 5)) x 4, 1..20;
    f "%2d" . ("  " . (" %4d" x 5)) x 4, $_, pairwise { $a *= $b } @a, @b for 1..30'

>          1%   2%   3%   4%   5%     6%   7%   8%   9%  10%    11%  12%  13%  14%  15%    16%  17%  18%  19%  20%
>    1    990  980  970  960  950    940  929  920  910  900    890  880  870  860  850    840  830  820  810  800
>    2    980  960  940  921  902    883  864  846  828  810    792  774  756  739  722    705  688  672  656  640
>    3    970  941  912  884  857    830  804  778  753  729    704  681  658  636  614    592  571  551  531  512
>    4    960  922  885  849  814    780  748  716  685  656    627  599  572  547  522    497  474  452  430  409
>    5    950  903  858  815  773    733  695  659  624  590    558  527  498  470  443    418  393  370  348  327
>    6    941  885  832  782  735    689  646  606  567  531    496  464  433  404  377    351  326  304  282  262
>    7    932  868  807  751  698    648  601  557  516  478    442  408  377  347  320    295  271  249  228  209
>    8    922  850  783  721  663    609  559  513  470  430    393  359  328  299  272    247  225  204  185  167
>    9    913  833  760  692  630    572  520  472  427  387    350  316  285  257  231    208  186  167  150  134
>   10    904  817  737  664  598    538  483  434  389  348    311  278  248  221  196    174  155  137  121  107
>   11    895  800  715  638  568    506  450  399  354  313    277  245  216  190  167    146  128  112   98   85
>   12    886  784  693  612  540    475  418  367  322  282    246  215  188  163  142    123  106   92   79   68
>   13    877  769  673  588  513    447  389  338  293  254    219  189  163  140  120    103   88   75   64   54
>   14    868  753  652  564  487    420  362  311  267  228    195  167  142  121  102     87   73   62   52   43
>   15    860  738  633  542  463    395  336  286  243  205    174  146  123  104   87     73   61   50   42   35
>   16    851  723  614  520  440    371  313  263  221  185    154  129  107   89   74     61   50   41   34   28
>   17    842  709  595  499  418    349  291  242  201  166    137  113   93   76   63     51   42   34   27   22
>   18    834  695  577  479  397    328  270  222  183  150    122  100   81   66   53     43   34   28   22   18
>   19    826  681  560  460  377    308  251  205  166  135    109   88   70   56   45     36   29   23   18   14
>   20    817  667  543  442  358    290  234  188  151  121     97   77   61   48   38     30   24   18   14   11
>   21    809  654  527  424  340    272  217  173  137  109     86   68   53   42   32     25   19   15   11    9
>   22    801  641  511  407  323    256  202  159  125   98     77   60   46   36   28     21   16   12    9    7
>   23    793  628  496  391  307    240  188  146  114   88     68   52   40   31   23     18   13   10    7    5
>   24    785  615  481  375  291    226  175  135  103   79     61   46   35   26   20     15   11    8    6    4
>   25    777  603  466  360  277    212  162  124   94   71     54   40   30   23   17     12    9    7    5    3
>   26    770  591  452  345  263    200  151  114   86   64     48   36   26   19   14     10    7    5    4    3
>   27    762  579  439  332  250    188  140  105   78   58     43   31   23   17   12      9    6    4    3    2
>   28    754  567  426  318  237    176  131   96   71   52     38   27   20   14   10      7    5    3    2    1
>   29    747  556  413  306  225    166  121   89   64   47     34   24   17   12    8      6    4    3    2    1
>   30    739  545  401  293  214    156  113   81   59   42     30   21   15   10    7      5    3    2    1    1

ISO Paper Sizes

ISO replaced 8 standards by one. Now we have 9 standards. :-(

Since @A(RGV) is initially empty, -A isn't looping. We can do other things as a side effect, rather than in a separate -B. Use Perl's lovely list assignment to swap and alternately halve the numbers. Because halving happens before echoing, start with double size:

pl -oA '($w, $h) = (1189, 1682); 0..10' \
    'form "A%-2d  %4dmm x %4dmm", $_, ($w, $h) = ($h / 2, $w)'
pl -oA '($w, $h) = (1189, 1682); 0..10' \
    'f "A%-2d  %4dmm x %4dmm", $_, ($w, $h) = ($h / 2, $w)'

>   A0    841mm x 1189mm
>   A1    594mm x  841mm
>   A2    420mm x  594mm
>   A3    297mm x  420mm
>   A4    210mm x  297mm
>   A5    148mm x  210mm
>   A6    105mm x  148mm
>   A7     74mm x  105mm
>   A8     52mm x   74mm
>   A9     37mm x   52mm
>   A10    26mm x   37mm

You could widen the table to cover B- & C-formats, by extending each list of 2, to a corresponding list of 6, e.g., ($Aw, $Ah, $Bw, ...). But a more algorithmic approach seems better. Triple the format (with cheat spaces at the beginning). The main program loops over @A(RGV), thanks to -O, doing the same as above but on anonymous elements of @d, which -A sets as a side effect:

pl -OA '@d = (["A", 1189, 1682], ["B", 1414, 2000], ["C", 1297, 1834]); 0..10' \
    'form "  %3s  %4dmm x %4dmm" x 3,
        map +("$$_[0]$ARGV", ($$_[1], $$_[2]) = ($$_[2] / 2, $$_[1])), @d'
pl -OA '@d = (["A", 1189, 1682], ["B", 1414, 2000], ["C", 1297, 1834]); 0..10' \
    'f "  %3s  %4dmm x %4dmm" x 3,
        map +("$$_[0]$A", ($$_[1], $$_[2]) = ($$_[2] / 2, $$_[1])), @d'

>      A0   841mm x 1189mm   B0  1000mm x 1414mm   C0   917mm x 1297mm
>      A1   594mm x  841mm   B1   707mm x 1000mm   C1   648mm x  917mm
>      A2   420mm x  594mm   B2   500mm x  707mm   C2   458mm x  648mm
>      A3   297mm x  420mm   B3   353mm x  500mm   C3   324mm x  458mm
>      A4   210mm x  297mm   B4   250mm x  353mm   C4   229mm x  324mm
>      A5   148mm x  210mm   B5   176mm x  250mm   C5   162mm x  229mm
>      A6   105mm x  148mm   B6   125mm x  176mm   C6   114mm x  162mm
>      A7    74mm x  105mm   B7    88mm x  125mm   C7    81mm x  114mm
>      A8    52mm x   74mm   B8    62mm x   88mm   C8    57mm x   81mm
>      A9    37mm x   52mm   B9    44mm x   62mm   C9    40mm x   57mm
>     A10    26mm x   37mm  B10    31mm x   44mm  C10    28mm x   40mm

ANSI Background;Foreground Color Table

What color is a mirror? It depends whom you ask. ;-)

You get numbers to fill into "\e[BGm", "\e[FGm", or "\e[BG;FGm" to get a color and close it with "\e[m". This shows two times twice 8 different colors for dim & bright and for background & foreground. Hence the multiplication of escape codes and of values to fill them.

This fills @A(RGV) in -A twice, the 2nd time looping over the 1st list, as though it came from the command line. It maps it to the 16-fold number format to print the header, swallowing every other number with 0-width. Then the main program loops over it pairwise with $A(RGV), thanks to -o2, to print the body. It duplicates numbers with (N)x2, once to go into the escape sequence, once to display them:

pl -o2A 1..8 -A '$_, $_+39, $_+8, $_+99' -B 'form "co:   bg;fg"."%4d%.0s"x16, @ARGV;
    $b = Form "\e[%dm%3d "x16, map +(($_)x2, ($_+60)x2), 30..37' \
    'form "%2d: %4d;   \e[%2:dm$b\e[m", @$_'
pl -o2A 1..8 -A '$_, $_+39, $_+8, $_+99' -B 'f "co:   bg;fg"."%4d%.0s"x16, @A;
    $b = F "\e[%dm%3d "x16, map +(($_)x2, ($_+60)x2), 30..37' \
    'f "%2d: %4d;   \e[%2:dm$b\e[m", @$_'

Terminal Rulers

If you need a ruler to better count the width of some other output, you can print out one of the following. These are either decimal, by groups of 5 or hex by groups of 4 and 8. The latter two do the same. But instead of one static ruler of length 100 or 256, they repeat and adapt. Depending on your terminal emulator and Shell, the variable $COLUMNS may track the current width. If so, pass it in a single argument to "loop" over with -o, else provide the desired width yourself:

pl 'say map "$_...:.....", 0..9'
pl 'say map "$_..:...|...:....", 0..9, "A".."F"'
pl -o 'say substr join( "", map "$_...:.....", 0..9 ) x ($_ / 100 + 1), 0, $_' $COLUMNS
pl -o 'say substr join( "", map "$_..:...|...:....", 0..9, "A".."F" ) x ($_ / 256 + 1), 0, $_' $COLUMNS

>   0...:.....1...:.....2...:.....3...:.....4...:.....5...:.....6...:.....7...:.....8...:.....9...:.....
>   0..:...|...:....1..:...|...:....2..:...|...:....3..:...|...:....4..:...|...:....5..:...|...:....6..:...|...:....7..:...|...:....8..:...|...:....9..:...|...:....A..:...|...:....B..:...|...:....C..:...|...:....D..:...|...:....E..:...|...:....F..:...|...:....
>   0...:.....1...:.....2...:.....3...:.....4...:.....5...:.....6...:.....7...:.....
>   0..:...|...:....1..:...|...:....2..:...|...:....3..:...|...:....4..:...|...:....

Math

Minimum and Maximum

The List::Util functions min and max are imported for you:

pl 'echo max 1..5'
pl 'e max 1..5'

>   5

If you have just several numbers on each line and want their minimums, you can autosplit (-a) to @F(IELD):

pl -a 'echo min @FIELD' file*
pl -a 'e min @FIELD' file*

If on the same you just want the overall minimum, you can use the print-at-end variable $R(ESULT), which you initialise to infinity in a -B begin program:

pl -aB '$RESULT = "inf"' '$RESULT = min $RESULT, @FIELD' file*
pl -aB '$R = "inf"' '$R = min $R, @FIELD' file*

Likewise, for overall maximum, you start with negative infinity:

pl -aB '$RESULT = "-inf"' '$RESULT = max $RESULT, @FIELD' file*
pl -aB '$R = "-inf"' '$R = max $R, @FIELD' file*

Median, Quartiles, Percentiles

The median is the number where half the list is less, and half is greater. Similarly, the 1st quartile is where 25% are less and the 3rd where 25% are greater. Use a list slice to extract these 3 and a 97th percentile, by multiplying the fractional percentage with the list length:

pl -A 0..200 'echo @ARGV[map $_*@ARGV, .25, .5, .75, .97]'
pl -A 0..200 'e @A[map $_*@A, .25, .5, .75, .97]'

>   50 100 150 194

If you'd rather have names associated, assign them to hash slice in sort-numerically-at-end %N(UMBER), whose key order must match the percentages. Note how <...> without wildcard characters is like qw(...):

pl -A 0..200 '@NUMBER{<lower median upper 97%>} = @ARGV[map $_*@ARGV, .25, .5, .75, .97]'
pl -A 0..200 '@N{<lower median upper 97%>} = @A[map $_*@A, .25, .5, .75, .97]'

>         50: lower
>        100: median
>        150: upper
>        194: 97%

Triangular Number, Factorial, and Averages

80% of people consider themselves to be above average. :-)

The triangular number is defined as the sum of all numbers from 1 to n, e.g., 1 to 5. Factorial is the equivalent for products:

pl 'echo sum 1..5;
    echo product 1..5'
pl 'e sum 1..5;
    e product 1..5'

>   15
>   120

The sum of all list elements divided by the length of the list gives the linear average. Alternately the root mean square can be a fairer average because it accounts for the weights:

pl -A 11..200 'echo sum( @ARGV ) / @ARGV;
     echo sqrt sum( map $_ ** 2, @ARGV ) / @ARGV'
pl -A 11..200 'e sum( @A ) / @A;
     e sqrt sum( map $_ ** 2, @A ) / @A'

>   105.5
>   118.905424602917

Add Pairs or Tuples of Numbers

If you have a list of number pairs and want to add each 1st and each 2nd number, reduce is your friend. Inside it map over the pair elements 0..1:

pl 'echo reduce {
        [map $a->[$_] + $b->[$_], 0..1]
    } [1, 11], [2, 12], [3, 13]'
pl 'e reduce {
        [map $a->[$_] + $b->[$_], 0..1]
    } [1, 11], [2, 12], [3, 13]'

>   [
>     6,
>     36
>   ]

If your list is a variable and is empty the result is undef. You can insert a fallback zero element if you'd rather receive that for an empty list:

pl 'echo reduce {
        [map $a->[$_] + $b->[$_], 0..1]
    } [0, 0], @list'
pl 'e reduce {
        [map $a->[$_] + $b->[$_], 0..1]
    } [0, 0], @list'

>   [
>     0,
>     0
>   ]

The above adds pairs because we iterate 0..1. You can generalize this to tuples by iterating to the length of the 1st array:

pl 'echo reduce {
        [map $a->[$_] + $b->[$_], 0..$#$a]
    } [1, 11, 21], [2, 12, 22], [3, 13, 23]'
pl 'e reduce {
        [map $a->[$_] + $b->[$_], 0..$#$a]
    } [1, 11, 21], [2, 12, 22], [3, 13, 23]'

>   [
>     6,
>     36,
>     66
>   ]

Big Math

2 + 2 = 5 for extremely large values of 2. :-)

With the bignum and bigrat modules you can do arbitrary precision and semi-symbolic fractional math:

pl -Mbignum 'echo 123456789012345678901234567890 * 123456789012345678901234567890'
pl -Mbignum 'e 123456789012345678901234567890 * 123456789012345678901234567890'

>   15241578753238836750495351562536198787501905199875019052100

pl -Mbignum 'echo 1.23456789012345678901234567890 * 1.23456789012345678901234567890'
pl -Mbignum 'e 1.23456789012345678901234567890 * 1.23456789012345678901234567890'

>   1.52415787532388367504953515625361987875019051998750190521

pl -Mbigrat 'echo 1/23456789012345678901234567890 * 1/23456789012345678901234567890'
pl -Mbigrat 'e 1/23456789012345678901234567890 * 1/23456789012345678901234567890'

>   1/550220950769700970248437984536198787501905199875019052100

Primes

This calculates all primes in a given range, e.g., 2 to 99:

pl 'echo grep {
        $a = $_;
        all { $a % $_ } 2..$_/2;
    } 2..99'
pl 'e grep {
        $a = $_;
        all { $a % $_ } 2..$_/2;
    } 2..99'

>   2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97

Fibonacci Numbers

These are, seeded with 1 and 1, all sums of the previous two. Show all up to a given maximum:

pl '$a = $_ = 1; echo;
    while( $_ < $ARGV[0] ) {
        echo; ($a, $_) = ($_, $a + $_)
    }' 50000
pl '$a = $_ = 1; e;
    while( $_ < $A[0] ) {
        e; ($a, $_) = ($_, $a + $_)
    }' 50000

>   1
>   1
>   2
>   3
>   5
>   8
>   13
>   21
>   34
>   55
>   89
>   144
>   233
>   377
>   610
>   987
>   1597
>   2584
>   4181
>   6765
>   10946
>   17711
>   28657
>   46368

Collatz 3n + 1

What's 3n plus n? Hmm, sounds 4n to me. (-:

Collatz' unproven & unrefuted conjecture is that the function f(n) = if odd: 3n + 1 else n/2 will always lead to 1, when applied repeatedly to any natural number n. Since if odd: 3n + 1 is even, we can skip it and go straight to the postsuccessor (3n + 1)/2 = (2n + n-1 + 2)/2 = n + int(n/2) + 1. Loop with -o over remaining args in $_. Having simplified the factor 3, inline the function as more efficient bit-ops:

pl -o 'echo "---" if $ARGIND; echo;
    while( $_ > 1 ) {
        if( $_ & 1 ) { ++($_ += $_ >> 1) } else { $_ >>= 1 }
        echo;
    }' 23 27
pl -o 'e "---" if $I; e;
    while( $_ > 1 ) {
        if( $_ & 1 ) { ++($_ += $_ >> 1) } else { $_ >>= 1 }
        e;
    }' 23 27

>   23
>   35
>   53
>   80
>   40
>   20
>   10
>   5
>   8
>   4
>   2
>   1
>   ---
>   27
>   41
>   62
>   31
>   47
>   71
>   107
>   161
>   242
>   121
>   182
>   91
>   137
>   206
>   103
>   155
>   233
>   350
>   175
>   263
>   395
>   593
>   890
>   445
>   668
>   334
>   167
>   251
>   377
>   566
>   283
>   425
>   638
>   319
>   479
>   719
>   1079
>   1619
>   2429
>   3644
>   1822
>   911
>   1367
>   2051
>   3077
>   4616
>   2308
>   1154
>   577
>   866
>   433
>   650
>   325
>   488
>   244
>   122
>   61
>   92
>   46
>   23
>   35
>   53
>   80
>   40
>   20
>   10
>   5
>   8
>   4
>   2
>   1

Add some fancy indent to show the turns, starting far enough right to let the snakes wiggle in both directions:

pl -o 'echo "---" if $ARGIND;
    $i = 40;
    while( 1 ) {
        form "%*d", $i, $_;
    last if $_ < 2;
        if( $_ & 1 ) { ++$i; ++($_ += $_ >> 1) } else { --$i; $_ >>= 1 }
    }' 15 48 49
pl -o 'e "---" if $I;
    $i = 40;
    while( 1 ) {
        f "%*d", $i, $_;
    last if $_ < 2;
        if( $_ & 1 ) { ++$i; ++($_ += $_ >> 1) } else { --$i; $_ >>= 1 }
    }' 15 48 49

>                                         15
>                                          23
>                                           35
>                                            53
>                                             80
>                                            40
>                                           20
>                                          10
>                                          5
>                                           8
>                                          4
>                                         2
>                                        1
>   ---
>                                         48
>                                        24
>                                       12
>                                       6
>                                      3
>                                       5
>                                        8
>                                       4
>                                      2
>                                     1
>   ---
>                                         49
>                                          74
>                                         37
>                                          56
>                                         28
>                                        14
>                                        7
>                                        11
>                                         17
>                                          26
>                                         13
>                                          20
>                                         10
>                                         5
>                                          8
>                                         4
>                                        2
>                                       1

Powers of 2 only get halved, so check only as long as the result has more than one bit on (n & (n - 1)). Furthermore, this tricky problem alternates between the binary & ternary realms which never meet, as no power of three is even. At least we can show both bases, their square and product bases, as well as, out of habit, decimal. For bases use bignum as of Perl 5.30, which would also allow astronomical numbers. Sadly, f(orm) can't go beyond 64 bits, so this is also how you'd get around that. Also add direction indicators:

pl -OMbignum -B 'form $f = "%s %26s %16s %14s %12s %9s %8s", " ", @b = <2 3 4 6 9 10>' '$ARGV += 0; $b = 2;
    echo "---" if $ARGIND;
    while( 1 ) {
        form $f, qw(\\ / +)[$b], map $ARGV->to_base($_), @b;
    last unless $ARGV & ($ARGV - 1);
        if( $b = $ARGV & 1 ) { ++($ARGV += $ARGV >> 1) } else { $ARGV >>= 1 }
    }' 255 511
pl -OMbignum -B 'f $f = "%s %26s %16s %14s %12s %9s %8s", " ", @b = <2 3 4 6 9 10>' '$A += 0; $b = 2;
    e "---" if $I;
    while( 1 ) {
        f $f, qw(\\ / +)[$b], map $A->to_base($_), @b;
    last unless $A & ($A - 1);
        if( $b = $A & 1 ) { ++($A += $A >> 1) } else { $A >>= 1 }
    }' 255 511

>                              2                3              4            6         9       10
>   +                   11111111           100110           3333         1103       313      255
>   /                  101111111           112012          11333         1435       465      383
>   /                 1000111111           210022          20333         2355       708      575
>   /                 1101011111          1011222          31133         3555      1158      863
>   /                10100001111          1202222         110033         5555      1688     1295
>   /                11110010111          2122222         132113        12555      2588     1943
>   /               101101100011         10222222         231203        21255      3888     2915
>   /              1000100010101         12222222        1010111        32125      5888     4373
>   /              1100110100000         22222222        1212200        50212      8888     6560
>   \               110011010000         11111111         303100        23104      4444     3280
>   \                11001101000          2020202         121220        11332      2222     1640
>   \                 1100110100          1010101          30310         3444      1111      820
>   \                  110011010           120012          12122         1522       505      410
>   \                   11001101            21121           3031          541       247      205
>   /                  100110100           102102          10310         1232       372      308
>   \                   10011010            12201           2122          414       181      154
>   \                    1001101             2212           1031          205        85       77
>   /                    1110100            11022           1310          312       138      116
>   \                     111010             2011            322          134        64       58
>   \                      11101             1002            131           45        32       29
>   /                     101100             1122            230          112        48       44
>   \                      10110              211            112           34        24       22
>   \                       1011              102             23           15        12       11
>   /                      10001              122            101           25        18       17
>   /                      11010              222            122           42        28       26
>   \                       1101              111             31           21        14       13
>   /                      10100              202            110           32        22       20
>   \                       1010              101             22           14        11       10
>   \                        101               12             11            5         5        5
>   /                       1000               22             20           12         8        8
>   ---
>   +                  111111111           200221          13333         2211       627      511
>   /                 1011111111          1001102          23333         3315      1042      767
>   /                10001111111          1120122         101333         5155      1518     1151
>   /                11010111111          2100222         122333        11555      2328     1727
>   /               101000011111         10112222         220133        15555      3488     2591
>   /               111100101111         12022222         330233        25555      5288     3887
>   /              1011011000111         21222222        1123013        42555      7888     5831
>   /             10001000101011        102222222        2020223       104255     12888     8747
>   /             11001101000001        122222222        3031001       140425     18888    13121
>   /            100110011100010        222222222       10303202       231042     28888    19682
>   \             10011001110001        111111111        2121301       113321     14444     9841
>   /             11100110101010        202020202        3212222       152202     22222    14762
>   \              1110011010101        101010101        1303111        54101     11111     7381
>   /             10101101000000        120012002        2231000       123132     16162    11072
>   \              1010110100000         21121001        1112200        41344      7531     5536
>   \               101011010000         10210112         223100        20452      3715     2768
>   \                10101101000          1220021         111220        10224      1807     1384
>   \                 1010110100           221122          22310         3112       848      692
>   \                  101011010           110211          11122         1334       424      346
>   \                   10101101            20102           2231          445       212      173
>   /                  100000100           100122          10010         1112       318      260
>   \                   10000010            11211           2002          334       154      130
>   \                    1000001             2102           1001          145        72       65
>   /                    1100010            10122           1202          242       118       98
>   \                     110001             1211            301          121        54       49
>   /                    1001010             2202           1022          202        82       74
>   \                     100101             1101            211          101        41       37
>   /                     111000             2002            320          132        62       56
>   \                      11100             1001            130           44        31       28
>   \                       1110              112             32           22        15       14
>   \                        111               21             13           11         7        7
>   /                       1011              102             23           15        12       11
>   /                      10001              122            101           25        18       17
>   /                      11010              222            122           42        28       26
>   \                       1101              111             31           21        14       13
>   /                      10100              202            110           32        22       20
>   \                       1010              101             22           14        11       10
>   \                        101               12             11            5         5        5
>   /                       1000               22             20           12         8        8

This lead to exciting findings here.

Separate Big Numbers with Commas, ...

Loop and print with line-end (-opl) over remaining args in $_. If reading from stdin or files, instead of arguments, use only -pl. After a decimal dot, insert a comma before each 4th commaless digit. Then do the same backwards from end or decimal dot, also for Perl style with underscores:

n='1234567 12345678 123456789 1234.5678 3.141 3.14159265358'
pl -opl '1 while s/[,.]\d{3}\K(?=\d)/,/;
    1 while s/\d\K(?=\d{3}(?:$|[.,]))/,/' $n
pl -opl '1 while s/[._]\d{3}\K(?=\d)/_/;
    1 while s/\d\K(?=\d{3}(?:$|[._]))/_/' $n

>   1,234,567
>   12,345,678
>   123,456,789
>   1,234.567,8
>   3.141
>   3.141,592,653,58
>   1_234_567
>   12_345_678
>   123_456_789
>   1_234.567_8
>   3.141
>   3.141_592_653_58

The same for languages with a decimal comma, using either a dot or a space as spacer:

n='1234567 12345678 123456789 1234,5678 3,141 3,141592653589'
pl -opl '1 while s/[,.]\d{3}\K(?=\d)/./;
    1 while s/\d\K(?=\d{3}(?:$|[.,]))/./' $n
pl -opl '1 while s/[, ]\d{3}\K(?=\d)/ /;
    1 while s/\d\K(?=\d{3}(?:$|[ ,]))/ /' $n

>   1.234.567
>   12.345.678
>   123.456.789
>   1.234,567.8
>   3,141
>   3,141.592.653.589
>   1 234 567
>   12 345 678
>   123 456 789
>   1 234,567 8
>   3,141
>   3,141 592 653 589

Web

HTML Encoding

Sometimes you need to en- or decode HTML entities, e.g. for HTML displayed in a <pre>. Only the 1st 2 characters are essential, but often these & < > " ' get encoded:

echo "<p class=\"example\">Planet pl's plucky &amp; pleasant plasticity</p>" |
    pl -pB '%ent = split /\b/, "&amp<lt>gt\"quot${q}apos";
        $ent = join "", keys %ent' \
        's/([$ent])/&$ent{$1};/go'
echo "&lt;p class=&quot;example&#x22;&#62;Planet pl&apos;s plucky &amp;amp; pleasant plasticity&lt;/p&gt;" |
    pl -pB '%ent = split /\b/, "amp&lt<gt>quot\"apos$q";
        $ent = join "|", keys %ent' \
        's/&(?:#x([0-9a-f]+)|#([0-9]+)|($ent));/$3 ? $ent{$3} : chr( $1 ? hex $1 : $2 )/egio'

>   <p class="example">Planet pl$qs plucky &amp; pleasant plasticity</p>
>   Planet pl's plucky & pleasant plasticity

URL Encoding

URL (or URI, or percent) encoding is used to embed arbitrary data, like another URL, into a URL. This makes it hard to read. So, let's decode it, also treating the non-standard, but widespread '+':

echo https%3a%2f%2frt%2ecpan%2eorg%2FDist%2FDisplay%2ehtml%3FStatus%3D%5F%5FActive%5F%5F%3BQueue%3DApp-pl |
    pl -p 'tr/+/ /;
        s/%([0-9a-f]{2})/chr hex $1/egi'

>   https://rt.cpan.org/Dist/Display.html?Status=__Active__;Queue=App-pl

Many characters pose no problem and are often left unencoded. But let's encode according to rfc3986, whereby only a very limited set of characters is exempt. Here -l matters, otherwise the newline would also get encoded:

echo 'https://rt.cpan.org/Dist/Display.html?Status=__Active__;Queue=App-pl' |
    pl -pl 's/[^0-9a-z~_.-]/Form "%%%02X", ord $&/egi'
echo 'https://rt.cpan.org/Dist/Display.html?Status=__Active__;Queue=App-pl' |
    pl -pl 's/[^0-9a-z~_.-]/F "%%%02X", ord $&/egi'

>   https%3A%2F%2Frt.cpan.org%2FDist%2FDisplay.html%3FStatus%3D__Active__%3BQueue%3DApp-pl

DNS Lookup

What do you call a sheep with no legs? A cloud. *;=;

The h(osts) function deals with the nerdy details and outputs as a hosts file. This canonically sorts the file by address type (localhost, link local, private, public), version (IPv4, IPv6) and address. You tack on any number of IP-addresses or hostnames, either as Perl arguments or on the command-line via @A(RGV):

pl 'hosts qw(perl.org 127.0.0.1 perldoc.perl.org cpan.org)'
pl 'h qw(perl.org 127.0.0.1 perldoc.perl.org cpan.org)'

>   127.0.0.1 localhost
>   139.178.67.96 perl.org
>   146.75.118.132 perldoc.perl.org
>   151.101.1.55 cpan.org
>   151.101.65.55 cpan.org
>   151.101.129.55 cpan.org
>   151.101.193.55 cpan.org
>   2a04:4e42:8d::644 perldoc.perl.org

pl 'hosts @ARGV' perl.org 127.0.0.1 perldoc.perl.org cpan.org
pl 'h @A' perl.org 127.0.0.1 perldoc.perl.org cpan.org

If you don't want it to merge & sort, call h(osts) for individual addresses:

pl 'hosts for qw(perl.org 127.0.0.1 perldoc.perl.org cpan.org)'
pl 'h for qw(perl.org 127.0.0.1 perldoc.perl.org cpan.org)'

>   139.178.67.96 perl.org
>   127.0.0.1 localhost
>   146.75.118.132 perldoc.perl.org
>   2a04:4e42:8d::644 perldoc.perl.org
>   151.101.1.55 cpan.org
>   151.101.65.55 cpan.org
>   151.101.129.55 cpan.org
>   151.101.193.55 cpan.org

pl -o hosts perl.org 127.0.0.1 perldoc.perl.org cpan.org
pl -o h perl.org 127.0.0.1 perldoc.perl.org cpan.org

If your input comes from files, collect it in a list and perform at end (-E):

pl -lnE 'hosts @list' 'push @list, $_' file*
pl -lnE 'h @list' 'push @list, $_' file*

Miscellaneous

There are various other examples here.

Renumber Shell Parameters

If you want to insert another parameter before $2, you have to renumber $2 - $8 respectively to $3 - $9. The same applies to Perl regexp match variables. This matches and replaces them, including optional braces. Apply in your editor to the corresponding region:

echo 'random Shell stuff with $1 - $2 - x${3}yz' |
    pl -p 's/\$\{?\K([2-8])\b/$1 + 1/eg'

>   random Shell stuff with $1 - $3 - x${4}yz

System Errors

Assign Unix error numbers to Perl's magic variable $!, which in string context gives the corresponding message. Instead of explicit individual numbers, you could fill @A(RGV) programmatically with -A 1..133 (the biggest errno on my system):

pl -o 'form "%3d %1:s", $! = $_' 1 14 64 111
pl -o 'f "%3d %1:s", $! = $_' 1 14 64 111

>     1 Operation not permitted
>    14 Bad address
>    64 Machine is not on the network
>   111 Connection refused

Find Palindromes

This assumes a dictionary on your machine. It loops over the file printing each match -P. It eliminates trivia like I, mom & dad with a minimum length:

pl -Pl 'length > 3 and $_ eq reverse' /usr/share/dict/words

>   boob
>   civic
>   deed
>   deified
>   kayak
>   kook
>   level
>   ma'am
>   madam
>   minim
>   noon
>   peep
>   poop
>   radar
>   redder
>   refer
>   rotor
>   sexes
>   tenet
>   toot

Generate a Random UUID

Lottery: a tax on people who are bad at math. :-)

This gives a hex number with the characteristic pattern of dashes. The hex format takes only the integral parts of the random numbers. If you need to further process the UUID, you can retrieve it instead of echoing, by giving a scalar context, e.g., $x = form ...:

pl '$x = "%04x";
    form "$x$x-$x-$x-$x-$x$x$x", map rand 0x10000, 0..7'
pl '$x = "%04x";
    f "$x$x-$x-$x-$x-$x$x$x", map rand 0x10000, 0..7'

>   9ed6347a-f52d-74eb-6f7f-609ea30ed42a

To be RFC 4122 conformant, the 4 version & 2 variant bits need to have standard values. As a different approach, -o "loops" over the one parameter in $_. This transforms the template into a format:

pl -o '@u = map rand 0x10000, 0..7;
    ($u[3] /= 16) |= 0x4000;
    ($u[4] /= 4) |= 0x8000;
    form s/x/%04x/gr, @u' xx-x-x-x-xxx
pl -o '@u = map rand 0x10000, 0..7;
    ($u[3] /= 16) |= 0x4000;
    ($u[4] /= 4) |= 0x8000;
    f s/x/%04x/gr, @u' xx-x-x-x-xxx

>   be9957bb-1c70-46c1-8530-db3f7fb17a93

Generate a Random Password

Why should you trust atoms? They make up everything. :-)

Use say, which doesn't put spaces between its arguments. Generate twelve random characters from 33 to 126, i.e., printable ASCII characters. Note that rand 94 will always be less than 94 and chr will round it down:

pl 'say map chr(33 + rand 94), 1..12'

>   3z(W=g)_$$9G

Just another pl hacker,

If you can't convince 'em, confuse 'em! ;-)

Just another Perl hacker, adapted. This obfuscated mock turtle soup JAPH is left for you to figure out. You may wonder y "y", y things start or end in "y":

pl -ploiy y' ya-zy You, Turtleneck phrase Jar. Yoda? Yes! 'y yhvjfumcjslifrkfsuoplie

>   Just another pl hacker,