You're 99% right, dws. As I've said before, obfuscation is quite often the masking of an abuse of the language, and this is abusing a bug that won't be present in the next version of Perl (I patched it yesterday, much to my amazement ;)).

The bug was that the $DIGIT variables were not COPIED when a pattern was done in list context; rather, they were "linked" to portions of the string. When the string changes, so do they (sometimes unpredictably). This won't occur in 5.6.1, because my patch removed that behavior, for one of two reasons: 1) it's not documented, and 2) it's not really useful, and could cause problems for people expecting the variables to behave normally.

If you remove the () = from the obfuscation, you'll see it doesn't "work".

japhy -- Perl and Regex Hacker