Rx (current version: 0.53; last updated 2001-02-28)

Rx is a backend for writing regex debuggers for Perl. It provides functions to do the following:

Decompile a Perl regex into a hash structure
Instrument a hash structure with callbacks that will be invoked during the execution of the regex
Recompile the modified hash structure back into Perl's internal regex format
Install compiled regexes into the Perl op tree

If you arranage that the callbacks will appropriately update a Tk window, you will have a graphical regex debugger. If the callbacks print out diagnostic information and prompt for a command before returning, you have a command-line regex debugger. These functions could be integrated into the standard Perl source debugger (perl -d) or into a standalone application.

Rx formed the basis for the regex debugger component of ActiveState's ASPN Komodo IDE. (Whether it still does, I can't say.) The Rx kit is released under the Artistic License courtesy of ActiveState.

Available Materials

Rx 0.53 source code
Early proof-of-concept Tk applications:
- Proof-of-concept #1
- Proof-of-concept #2
Rx: A Regex Debugger for Perl. My award-winning paper about the internals of Rx. If you're planning to use Rx, this is all the documentation there is at present. However, it is reasonably complete.

Rx is not yet a complete, end-user application; it is a kit for building such applications. If you built a complete regex debugger application using Rx, please let me know so that I can mention it here.

What's New in 0.53

0.53 is the initial release

A Note About Working with ActiveState

For some reason several people have told me that they detected a negative tone in the remarks about ActiveState in my paper. These inferences took me completely by surprise. I think these people have overactive imaginations, or perhaps it's just the ingrained distrust that people in our community have for anything commercial. (An anecdote: When I was working on the proposal for the comp.lang.perl.moderated newsgroup, I asked Tim O'Reilly to endorse it; people then saw this is part of a conspiracy by O'Reilly to control the newsgroup. Some people will see an evil conspiracy anywhere.)

ActiveState released Komodo in 2000, but I waited another year to release Rx. Some people have jumped to the conclusion that big bad ActiveState was pushing me around, preventing my from releasing the free package, for their own commercial interests. This is not true at all. I postponed the free release voluntarily. I wanted them to have an opportunity to establish their product. Nobody at ActiveState asked me to do this; it was solely my own idea. For all I know, they didn't even care. As I said, some people see a conspiracy anywhere.

I will make the clearest statement that I can: In the paper I said that AS was a pleasure to work with, and that is true; the project was an overwhelmingly positive experience. I neither implied nor intended to imply any criticism of ActiveState in the paper, and none should be inferred. I will add, also, that they paid me with promptness that I have found unusual in a company of their size.

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