#!/usr/bin/perl

$t1 = '7:30';  #minimum time
$t2 = '11:45'; #maximum time
@t1 = split(':', $t1);
@t2 = split(':', $t2);

$interval = 15;  #may be (10,15,20,30)

 #create an array of intervals
for (0..(60/$interval)-1) {
  $mins[@mins]=(($_*$interval) ? $_*$interval : '00');
}

 #loop for number of hours requested
for ($t1[0]..$t2[0]) {
   #loop for number of intervals in array
  foreach $mins (@mins) {
     #print if min <= result <= max
    if ($_<=$t2[0]&&$mins<=$t2[1]) {
      print "$_:$mins\n" if (!($_==$t1[0]&&$mins<$t1[1]))
    }
  }
}