If you have more arguments than will usually fit on one (72-column, say) line, or if you expect that a function's arglist will change quite a bit over time, then named params are the way to go. Mostly, I try to avoid long arglists (I don't really use Perl's OO system, although one might say that I tend to write object-oriented code); anything that's hard to work with (like a long arglist) is a red flag for me, and I try to break it up into easy to work with pieces.
Yours in pedantry,
"Anything you put in comments is not tested and easily goes out of date." -- tye