#!/usr/bin/perl

use File::Find;

@ARGV = ('.') unless @ARGV;

$dir = shift @ARGV;

find( \&edits, $dir );

sub edits() {

    return unless -f;    #skip directories

    $seen = 0;
    $file = $_;

    #Uncomment next line if you want multi-line edits
    #undef $/;

    local $^I = ".backup";

    #Warning - heavy magic here
    local @ARGV = ($file);

    while (<>) {

        #Remember to use the s option if doing multiline edits
        $seen++ if s/Lesson/Chapter/;

        print;

    }

    print "Found in $File::Find::name\n" if $seen > 0;

    #Comment out if you want to keep the backup
    #unlink $file.".backup";

}