I think #1 could potentially buy you quite a bit. Subroutine overhead in Perl is quite large - lots of stack operations resulting in lots of memory reads and writes. I also think this is probably the one that might be possible in Perl 5. At the core it seems that it would require nothing worse than some really clever op-tree gymnastics...

I'm not smart enough to understand #2 yet. Someone needs to write the currying section in Learning Perl before I can grok it, perhaps.

What do you mean by #3? Filter?

-sam