Considering the sub is recursive and NEVER exits, is this really that surprising? The variables $number and $divisor are in the same address in memory the entire time (just print a ref to them and compare the addresses during every pass). The problem you are encountering is that a new call to the sub is getting pushed onto the internal stack with each call and never getting popped.

antirice    
The first rule of Perl club is - use Perl
The ith rule of Perl club is - follow rule i - 1 for i > 1