I can only judge the implementation, which considers $1 ff to be global.

update

This demonstrates whats happening, $2 is always the next character or empty.

  DB<322> ;m/ ^ .*? (?{say "<$_ $2>"})  (.) (?=(.|$)) (*FAIL)/x
<babab >
<babab a>
<babab b>
<babab a>
<babab b>
<babab >
[download]

You're asking theoretical questions, and then getting bogged down in current implementation.

Turn this around. What would you want to happen if you had a forward reference?

-QM
--
Quantum Mechanics: The dreams stuff is made of

You seem to think it's a bug, for me it's most likely a feature.

I think this stems from the foundations of regular expressions as state machines.

> What would you want to happen if you had a forward reference?

Something wonderful, HAL!

Cheers Rolf
_{(addicted to the Perl Programming Language and ☆☆☆☆ :)
Je suis Charlie!}