Eirik Hoem has pointed out an online tool a coworker shared with him to work with regular expressions for multiple languages.

A coworker of mine has been working on a ajax enabled regex tool which lets you evaluate regex expressions in several languages (including PHP PCRE and PHP POSIX) with instant results.

The tool lets you put in the string you want to match again and the pattern you want to match with. The results are automatically populated below it, making it easy to fine-tune your expression to only what you want.

Sean Coates has created a simple version of a popular bit of Perl functionality and shares the code in hi slatest post - the "pie" ability to perform a search and replace, line by line, through a file using a regular expression.

I've often found myself looking for a PHP equivalent. Not to do simple substitutions, of course, but complex ones. And since I'm most comfortable with PHP, and a I have a huge library of snippets that I can dig out to quell a problem that I may have solved years ago, I've been meaning to fill this void for a while.

So, one evening, he came home and hashed out this version of the script. He includes the code in the post...it works on the command line and pulls in a file (though STDIN) and loops through the buffered version to perform the regex replace.