#!/usr/bin/perl

use File::Basename ();

sub basename {
  @array = split(/615/,$_[0]);
  return $array[0];
}

$filename="/courses/09/615/L615.txt";
$myown_basename = &basename($filename);
                  # calls some function I wrote
print "Basename of this file is possibly: $myown_basename\n";

$basename = File::Basename::basename $filename;
            # calls File::Basename's function
print "Basename of this file is: $basename\n";