Search and Replace Across Multiple Files with Perl

#!/usr/bin/perl -w
use strict;
 
=head1 NAME
 
Search and Replace
 
=head1 SYNOPSIS
 
    perl search-replace.pl <files>
 
=head1 DESCRIPTION
 
Search and replace against a hard-coded regex.  We'll use this script
to replace JavaScript image paths.  Maybe later it can
be adapted into something more flexible.
 
=head2 Caveats
 
Silent in-place replacement without backup.  Back up your assets (in
source control) before testing this script.
 
=head2 The original one-liner
 
    perl -pi.bak -e 's/("http:\/\/images.example.com)([^:?<>]+\.(gif|jp(e)?g|png))/"\047 + \$.example.foo + "$2" + \047/g' global.js
 
=cut
 
$^I=".bak";    # change the files themselves instead of writing to STDOUT
               # use 'bak' as the extension for backup files
 
while (<>)
{
   s{
          "http://images.example.com              # match a double quote, followed by
                                                  # the hard-coded URL we want to replace
 
        (                                         # now start capturing to the $1 backreference variable
 
          [^:?<>]+                                # match any character except those not legal in file paths
 
          \.                                      # followed by a literal dot, followed by
 
          (gif|jp(e)?g|png)                       # any of the usual image file extensions
 
        )                                         # stop capturing
 
     }{"' + \$.example.foo + '$1}xg;              # print back a properly quoted JavaScript string of the form:
                                                  #     ' + $.example.foo + "<pathname>" + '
 
   print $_;
}