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

use constant OLD => "CPB.old";
use constant NEW => "CPB";

use File::Find;

my $old_flag = 0;

find (
    {
        preprocess  => sub {
            print "Pre-Processing\n";
            $has_old = grep /\.old$/, @_;
            @_;
        }, 
        wanted      => sub {},
        postprocess => sub {
            print "Post-Processing\n";

            return unless $has_old;
            return unless rename NEW, OLD;

            open my $in, "<",  OLD
                or die "Unable to open input CPB: $!";

            open my $out, ">", NEW
                or die "Unable to open output CPB: $!";

            while (<$in>) {
                s!^cat\t!cat\t/kat/src/all/bld_pipe.4go \\\n\t!;
                print $out $_;
            }
        }
    }, 
    '/home/greg/mydir'
);