You might be better off using a module; that way, you don't have to deal with all the edge cases. 

#!/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

[download]

Output: 

former_time is 12:50:00
new time is 13:05:00
former_time is 05:49:00
new time is 06:04:00
former_time is 11:03:00
new time is 11:18:00
former_time is 15:09:00
new time is 15:24:00
former_time is 04:23:00
new time is 04:38:00
former_time is 08:34:00
new time is 08:49:00

[download]

--
"Language shapes the way we think, and determines what we can think about."
-- B. L. Whorf

In reply to Re: problem of configration by oko1
in thread problem of configration by steph_bow

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