#!/usr/local/bin/perl

use strict;
use warnings;
use File::Find;

my @argv;
my $dir = $ARGV[0];

find(\&recursiveDir, $dir);

sub recursiveDir{
        return if -d;
        my @files = glob "${dir}/*pl";
        foreach (@files) {
        next if -d;
        (my $txt = $_) =~ s/pl$/txt/;

        rename($_, $txt);

        }
}