my @sub_locs = grep { $_ } map { /taxman\.add\.subloc\.(.*)/ } @sessio
+n_keys;
[download]

Maybe a "bit more intuitive", but "wrong" if the value after taxman string might be empty or the value "0". Did you mean instead:

my @sub_locs = grep { defined $_ } map { /taxman\.add\.subloc\.(.*)/ }
+ @session_keys;
[download]

perhaps?

And of course, as I'm seeing this, the grep isn't even necessary, since on a failed match, the match returns an empty list!

my @sub_locs = map { /taxman\.add\.subloc\.(.+)/ } @session_keys;
[download]

is enough!

-- Randal L. Schwartz, Perl hacker