refactoring inherited code can be scary, unless you have a good set of tests for all the use cases the code needs to handle. Think of it as a safety net before you start. Also, a version control system would be useful in case of unintentional destructive changes...

So this should be the foundation to build on and the first step.

Once you have that, I would start refactoring with the help of Damian Conways' book 'Perl best practices' and the Perl-Critic tool. Keep the amount of changes small and focused, and retest often. Always before checking into version control.

Regarding your code snippet: assigning one variable to another one at least has the benefit of having more meaningful variable names (which makes it more user friendly, but is a bit redundant). Why not use good names in the first place?

Passing subroutine parameters in a hash, where the keys name the parameters, can also yield readable code, since the names are part of the subroutine interface then.

I hope this helps a bit.