IMHO sounds like far less than 1‰ of all CPAN modules might rely on this.

OK found another use-case, I just recently had the need in my ORG-Parser to distinguish the range delimiters and the range "body" with a flip-flop-operator, like for ORG's "BEGIN/END"-blocks.

This can be simplified (i.e. more DRY), if one has access to the last successful pattern:

  DB<114> for(0..99) {print if (/10/../20/ and not //)}
111213141516171819
  DB<115> for(0..99) {print if (/10/../20/)}
1011121314151617181920
  DB<116> for(0..99) {print if (/10/../20/ and //)}
1020
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I think that's a more frequent application, I even slightly remember seeing it in Friedl's book.

But I'd rather prefer an explicit special varą, something like $PATTERN or $&& (in analogy to $MATCH resp. $&) .

1) an special var has the advantage that the regex itself can be accessed, e.g. printed.