NAME

perlcheat - Perl 5 Cheat Sheet

DESCRIPTION

This 'cheat sheet' is a handy reference, meant for beginning Perl programmers. Not everything is mentioned, but 194 features may already be overwhelming.

The sheet

CONTEXTS  SIGILS             ARRAYS        HASHES
void      $scalar   whole:   @array        %hash
scalar    @array    slice:   @array[0, 2]  @hash{'a', 'b'}
list      %hash     element: $array[0]     $hash{'a'}
          &sub
          *glob    SCALAR VALUES
                   number, string, reference, glob, undef
REFERENCES
\     references      $$foo[1]       aka $foo->[1]
$@%&* dereference     $$foo{bar}     aka $foo->{bar}
[]    anon. arrayref  ${$$foo[1]}[2] aka $foo->[1]->[2]
{}    anon. hashref   ${$$foo[1]}[2] aka $foo->[1][2]
\()   list of refs
                        NUMBERS vs STRINGS  LINKS
OPERATOR PRECEDENCE     =          =        perl.plover.com
->                      +          .        search.cpan.org
++ --                   == !=      eq ne         cpan.org
**                      < > <= >=  lt gt le ge   pm.org
! ~ \ u+ u-             <=>        cmp           tpj.com
=~ !~                                            perldoc.com
* / % x                 SYNTAX
+ - .                   for    (LIST) { }, for (a;b;c) { }
<< >>                   while  ( ) { }, until ( ) { }
named uops              if     ( ) { } elsif ( ) { } else { }
< > <= >= lt gt le ge   unless ( ) { } elsif ( ) { } else { }
== != <=> eq ne cmp     for equals foreach (ALWAYS)
&
| ^              REGEX METACHARS            REGEX MODIFIERS
&&               ^     string begin         /i case insens.
||               $     str. end (before \n) /m line based ^$
.. ...           +     one or more          /s . includes \n
?:               *     zero or more         /x ign. wh.space
= += -= *= etc.  ?     zero or one          /g global
, =>             {3,7} repeat in range
list ops         ()    capture          REGEX CHARCLASSES
not              (?:)  no capture       .  == [^\n]
and              []    character class  \s == [\x20\f\t\r\n]
or xor           |     alternation      \w == [A-Za-z0-9_]
                 \b    word boundary    \d == [0-9]
                 \z    string end       \S, \W and \D negate
DO
use strict;        DON'T            LINKS
use warnings;      "$foo"           perl.com
my $var;           $$variable_name  perlmonks.org
open() or die $!;  `$userinput`     use.perl.org
use Modules;       /$userinput/     perl.apache.org
                                    parrotcode.org
FUNCTION RETURN LISTS
stat      localtime    caller         SPECIAL VARIABLES
 0 dev    0 second     0 package      $_    default variable
 1 ino    1 minute     1 filename     $0    program name
 2 mode   2 hour       2 line         $/    input separator
 3 nlink  3 day        3 subroutine   $\    output separator
 4 uid    4 month-1    4 hasargs      $|    autoflush
 5 gid    5 year-1900  5 wantarray    $!    sys/libcall error
 6 rdev   6 weekday    6 evaltext     $@    eval error
 7 size   7 yearday    7 is_require   $$    process ID
 8 atime  8 is_dst     8 hints        $.    line number
 9 mtime               9 bitmask      @ARGV command line args
10 ctime  just use                    @INC  include paths
11 blksz  POSIX::      3..9 only      @_    subroutine args
12 blcks  strftime!    with EXPR      %ENV  environment

ACKNOWLEDGEMENTS

The first version of this document appeared on Perl Monks, where several people had useful suggestions. Thank you, Perl Monks.

A special thanks to Damian Conway, who didn't only suggest important changes, but also took the time to count the number of listed features and make a Perl 6 version to show that Perl will stay Perl.

AUTHOR

Juerd Waalboer <juerd@cpan.org>, with the help of many Perl Monks.

SEE ALSO

http://perlmonks.org/?node_id=216602      the original PM post
http://perlmonks.org/?node_id=238031      Damian Conway's Perl 6 version
http://juerd.nl/site.plp/perlcheat        home of the Perl Cheat Sheet