Updated

this may help you

#!/usr/bin/perl -w

use strict;
use warnings;

my $input = 'All the following should be acceptable: 12:00am, 5:00pm, 
+8:30AM. These should probably not be accepted: 3:00,2:60am, 99:00am, 
+3:0pm, 29:00AM.';
while ($input =~ m/\W([1-9]|[01][0-2]|2[0-3]):[0-5][0-9][ap]m/gsi)
{
        print "This is a valid time!\t$&\n";
}
__END__
OUTPUT

This is a valid time!    12:00am
This is a valid time!    5:00pm
This is a valid time!    8:30AM
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