Long term, functions shouldn't take 10 parameters (that's ugly even in C...structures are a good way to fix this), and in Perl named variables (through use of hashes) are a good way to fix this.

do_wacky_stuff(
  -alpha => 1,
  -delta => 'sputnik',
  -beta => 2,
  -gamma => 3,
);
[download]

Note order doesn't matter, and that's why it's cool. Use Params::Validate for added fun-ness.

Also you mentioned inherited code being the root of all your problems. Such is life! My handwritten-from-scratch code doesn't have any bugs! SCENE 42: flyingmoose is striken dead by a lightingbolt from the heavens, onlookers seem puzzled as he was indoors!

oming from a more formal (ADA, Java) background I would favour a return

Perl is as formal as you make it. I prefer to call those languages 'whiney' not 'formal'. Why? Well you can just as easily screw up a Java app, and it takes discipline no matter what you do. Other languages just want to hamper your productivity more than others :)