use strict;
use warnings;
use Time::Piece;
use CGI qw(popup_menu);

my $time  = localtime;
my @month = $time->mon_list;

print popup_menu(
   -name     => 'month',
   -values   => [0..11],
   -default  => $time->_mon,
   -labels   => { map {($_ => $month[$_])} 0..11 },
);