The numbered match variables ($1, $2, $3, etc.) and the related punctu-
       ation set ($+, $&, $`, $', and $^N) are all dynamically scoped until
       the end of the enclosing block or until the next successful match,
       whichever comes first.  (See "Compound Statements" in perlsyn.)

       NOTE: failed matches in Perl do not reset the match variables, which
       makes easier to write code that tests for a series of more specific
       cases and remembers the best match.