Going back to your original question;
You can do this:

$a='aa';
$b='s/a/b/';
eval '$a =~ '.$b;
[download]

That means you can write:

my $namematch = $options{r} // 's/\.[^.]+$/+/r';
my @name;
eval '@name = $file =~ '.$namematch;
[download]

But you're basically just having Perl write Perl for you. This may be what you want.
SANITIZE YOUR INPUT. The value in $options{r} could be used for injection.

HTH.