Regexps are already closures via the ??{ construct. You just can't jump back into regexp because the engine isn't re-entrant (though I hear it works a bit - I seem to fall over all the nasty bits). What I'm really pining for are:
- Grammars for binary data (P::RD chokes)
- Being able to locally redefine the language
- Getting full access to the VM and in a meaningful way since perl5's VM is so clunky to work with
- Junctions!
- Lazy pipelining
- Co-routines
And I want these not because they're cool but because at various points I could have made my own code simpler, more efficient or had some otherwise significant improvement.