#!/usr/bin/perl -w
use strict;

my $new = "new text here!\n";

my $data_pos = tell DATA;

open SELF, "+<$0" or die "open $0: $!\n";

truncate SELF, $data_pos or die "truncate: $!\n";

seek SELF, 0, 2 or die "seek: $!\n"; # append now.

print SELF "$new" or die "print: $!\n"; # just in case

close SELF or die "while closing $0: $!\n";

__DATA__
this is the stuff to replace