In Perl, the number 0 is use for the false boolean and any number other than 0 is used for the true boolean.

This script will print false.

#!/usr/bin/perl
use strict;
use warnings;

my $boolean = 0;

if ($boolean) {
  print "true \n";
}
else {
  print "false \n";
}

Whereas this script will print true.

#!/usr/bin/perl
use strict;
use warnings;

my $boolean = 1;

if ($boolean) {
  print "true \n";
}
else {
  print "false \n";
}