First off: always use strictures (use strict; use warnings; - see The strictures, according to Seuss). There are a huge number of variables in you code fragment that may be global, but it is impossible to tell and impossible to tell what the nature of their contents ought to be if they are global. So, first off use strictures and lexical variables (declare them with my). If that doesn't resolve your issue by pointing out some silly lifetime issue, reduce the code to a runnable sample that demonstrates the problem.

Note that you sample should provide any required data in a variable or in the __DATA__ section (and not much of it).

@names = $new_gecos; looks suspect to me.

Why do you need to chomp @exact_match?