Can anybody ellaborate on this statement by Ovid. This small side note is interesting to me and i want to know more. I'm always interested in speeding up perl.

"As a small side note, be aware that providing a block or subroutine to the sort function will automatically slow down its performance as is will no longer be relying on straight C code to perform the sort. Naturally, I rarely feel it's necessary to consider this issue, but it's nice to know"

Why is it not straight C code? What is it?

Does this apply to any subroutine, or is 'sort' a special case?

Also, does the same issue hold true under mod_perl?

This reminds me of the rumor i heard that case non-sensitive pattern matching is particularly slow (/foo/i). Any ideas on how i could find out more about perl syntax and speed?