This is difficult subject to discuss without histrionics. I mentioned on the CB one day that I try to avoid the use of $_ because I think it makes code harder to read, and it was not a very popular notion.
Most of the advanced people on this site would certainly prefer eduardo's version, but my experience has been that many of the people I have to work with every day just don't know Perl well enough to quickly grok stuff like $frequency{$_}++ for (split /\W/, <>) quickly. Because of this, I try to stick to the more standard control structures when I can, and especially avoid stacking up a lot of operations on one line.
I still use things like map, grep, hash slices, and extended regular expressions, but not when something simpler will work with similar efficiency.
