in reply to using a subroutine

I would characterize a subroutine as a self-contained set of operations, performed on the arguments passed to it. opendirs sets the variable filehandle specified in the first argument, setting it to access the file system directory specified in the second argmument. unlink removes the file specified in its argument. rand(2) does something, and rand(100) does something similar but different, dependent on the different arguments. In particular, routines should be testable in isolation or in small groups.

So while you're doing well to use subroutines, if they are dependent on global variables then you're really writing one global, interconnected set of code. Addmittedly, in certain circumstances you may have global configuration variables, our $PI=3.14; or our $DEFAULT_SEPARATOR = ','; but that's a slightly different case .... but do try to avoid even those if you can.

As far as the list assignment:

my ($user, $lib) = qw(/home/john /lib);
is concerned, it works perfectly well:
my ($user, $lib) = qw(/home/john /lib); + print "\$user is '$user'.\n"; print "\$lib is '$lib'.\n"; # # Generates the output: # $user is '/home/john'. $lib is '/lib'.