|Do you know where your variables are?|
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:
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.
for limitations see update in Re^2: Extract table from a block of text (updated)