The $n is not needed ...

then the whole expression may be written more compact:

   ...
   my ($street, $number) = $address =~ /(.+?)             # first grou
+p
                                        (?:\s+ nr \.)?    # any number
+ prefix?
                                        \s+ [A-z]+ (\d+)  # number fol
+lows alpha
                                       /xi;
   print "STREET: $street, NUMBER: $number\n";
   ...
[download]

(although it might backtrack more now ;-)

Regards

mwa