#!/usr/bin/perl -w
use strict;
use Time::Simple;

for (<DATA>){
    s/(..)$/:$1/;
    my $former_time = Time::Simple->new($_);
    my $new_time = $former_time + 15 * 60;
    print "former_time is $former_time\nnew time is $new_time\n";
}

__DATA__
1250
0549
1103
1509
0423
0834