merlyn's reference to "Code Smell" (Wikipedia) comes from recent (~8 years) software development vocabulary. I do not believe he intended it to be derogatory.

Regarding your issue:
Use of uninitialized value $_[0] in string eq at ***** line 63, <> line 2
This is a result of your call:
vlan_number();
on line 118.

That call does not pass any parameters to "vlan_number():.

When you request $_[0], at line 62, it asks for the first parameter in @_;
Since @_ (Parameter list) is empty, you get the warning.