Just so you know... $1 et all are basically ties that do something like

substr($something, $-[$digit], $+[$digit] - $-[$digit]);
[download]

Part of the reason for this is that internally perl doesnt populate $1 et all with copies when it runs the regex as when backtracking it could have to recopy the contents of these vars many many times. Wheras updating the appropriate offsets is cheap and constant time.