That doesn't even make sense. There's not a uniform meaning of string subtraction. If you'd answer my sample problems above, it would help. There's *not* a unique way. You have to decide and tell us if you want us to help you. You tell us by giving lots of good examples, not one bad one. This isn't a Perl problem, it's a failure to clearly specify intended results problem, which is language independent.

Further, the gurus *did* share information with you, and you rejected all of it.