(...) if you can't explain precisely why you are using ampersands in your subroutine calls then leave them off (...)

Because ampersands make it clear to everyone that you know you're using a user-defined function rather than a builtin, and when used with parens don't do anything out of the ordinary (viz. (tye)Re: A question of style)?

I use ampersands everywhere I call user functions. It fits in nicely with the Perlish idea of "every symbol that isn't part of the language has a glyph" --- actually, now that I type that, I'm not certain that it's true, but it's mostly true so I stand by my coding style. Anyways, as tye points out, ampersands and parens Is Your Friend.