search-replace.pl

#!/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 $_;
}