Actually, every new function that has been introduced caused worries about possible name collisions. The Perl 5 development crowd is very conscientious about backward compatibility. This concern and the strong culture of testing are probably the best things Perl has going for it (in addition to CPAN and its innate awesomeness, of course). Contrast this with Python (as an example), where the breaks they introduced going from 2.8 to 3.0 have caused large swaths of their community to have two different copies of the Python interpreter installed on their systems.