Aha. I knew someone must have had the same general idea before! Thank you for that link. I only have a tiny gripe with it vs. my ideal verifier, which is that Params::Validate only validates, where as what I wrote above would imply validation and returning of the validated parameters (rolling two operations into one).

I'm certainly not about to reinvent a wheel over something so minor, though. The module you recommended will work nicely. Thanks again!

Update: this is what I get for merely scanning the POD before posting. As xdg points out, Params::Validate does everything I have wished for:

use Params::Validate;

sub foobar {
    my ($foo, $bar) = validate_pos ( @_, {type = SCALAR, regex=>/.+/},
                                         {type = HASH_REF} );
    
    print "Using $foo:\n";
    return $foo unless %$bar;
    for (keys %$bar) { print "$_ => $$bar{$_}\n" }
    return $$bar{'result'};
}
[download]

is equivalent to my earlier code.