use strict;
use warnings;

my $xcltime = "00:45:34"; # It should print 12:45 AM

my ($h, $m) = split /:/, $xcltime;

my $ampm = $h < 12 ? 'AM' : 'PM';
$h = ($h % 12) || 12;
print "$h:$m $ampm"; # prints 12:45 AM