in reply to Simple question about namespaces
If you have package variables in either of the two packages, the other will be able to read or write on them. For exemple you could have in a.pl :
$SUBS::option = getOption(); and if you declare our $option in the package SUBS, it will be the same variable.
If neither files have a package statement, then all variables declared by our will be in package Main, a variable declared our $option in one file will be the same as our $option in the other.
If you feel that messing around with another package's variables isn't clean enough, you could write accessor subs to get and set them.