Yes, "fix" was overstating the case somewhat in light of the level of understanding involved.

Take a look the this discussion. It's the same problem. The issue is that the compilation of the (?{...}) in the regex creates a closure on %mv and the second time through the sub the my %mv; creates a different instance of %mv which is not the one the regex is using.

Now I've told the teddy bear I understand the problem and why our works - at least until I get back to my desk. :)