Did you get the answer you wanted about the issue of "optional" parameters? Is this the kind of thing you're after?

# caller:
StartCapture( { twigs => {filter => $filterTwig, capture => $captureTw
+ig},
                hashes => {filter => \%filterHash, capture => \%captur
+eHash},
                files => {filter => 'filter.txt', capture => 'capture.
+txt'},
                results => 'c:/temp.txt' } );

# ...

sub StartCapture
{
    my $hashref = shift;

    $$hashref{results} ||= 'c:/SomeDefault.txt';

#   ...
}
[download]

Using the "||=" operator, the LHS (hash element in this case) will be assigned the RHS value iff the original LHS evaluates to false. (I believe that the most recent perl version also has a "//=" operator, which makes the assignment only if the LHS is undef, as opposed to being zero or an empty string.)