I don't think you can get what you're asking for, because I don't think apache provides it. When I want to know which location I matched, I do something like this:

<Location /blah>
  PerlSetVar matched "blah"
</Location>
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And then in my handler:

if ($r->dir_config('matched') eq 'blah') {
[download]

That serves my needs. However, if you want a definitive answer about whether this can be retrieved directly from apache or not, you need to ask on the mod_perl mailing list.