Re: Re: List-to-Range generation

[japhy]

Almost.

m{
  (\d+)           # \1 start -- digits -- \1 end
  (?:
    ,             # ,
    (             # \2 start
      (??{$++1})  # evaluate '$+ + 1' as a regex
    )+            # \2 end (and try again)
  )
}

The $+ refers to the last successful captured pattern, and that capture must have been closed. So the first time the (??{...}) is reached, $+ is $1's value. The next time, it's $2's (first) value, and then $2's new value, and so on.

japhy -- Perl and Regex Hacker