USE
All field keywords beginning with html_form_
are passed directly into the form hash. Thus, they are really defined in form.tt which ships with Gantry.
html_form_optional
is a boolean that, if true, allows the user to leave the field blank.
EXAMPLE
To see an example, build:
bigtop -c example.bigtop all
Change to the newly created Kids directory and look in the form method in lib/Kids/GEN/Child.pm.