use strict;
use warnings;

my $to_find = 'Pretty Woman';

while ( <DATA> ) {
   if ( /$to_find:\s*(\d+)/ ) {
      print "Slot for $to_find: $1\n";
   }
}

__DATA__
Label     Location                        Start Time  End Time
NKL0289   MSL6000 Trinity: 7              18:45       20:45
NKL0111   MSL7000 A Fish Called Wanda: 22 11:11       13:00
XKL0ABCC  MSL8000 Pretty Woman: 55        18:13       20:12