Most programming languages have a native 'Boolean' data type. Perl does
not.

Perl has a simple and well known Truth System. The following scalar values
are false:

$false1 = undef;
$false2 = 0;
$false3 = 0.0;
$false4 = '';
$false5 = '0';

Every other scalar value is true.

This module provides basic Boolean support, by defining two special
objects: 'true' and 'false'.