#!/usr/local/bin/perl
# Jaime Prilusky, 2004

  my $string = $ARGV[0] || "abcedefghijklmnopqrstuvwxyz";

print "original $string";

  my $replacement = "SOMETHING DIFFERENT";
  my $portion = substr($string,4,10,$replacement);

  print qq{
original $string
portion  $portion
};