That's a very good point. And in situations where a seperate sub may be inconvenient, an enclosing lexical block can be helpful:

use strict;
use warnings;

my $var = 10;
{
    my $var = 20;
    print $var, "\n";
}
print $var, "\n";

__OUTPUT__
20
10
[download]

...just a quick demonstration of using {...} blocks to limit scope and protect variables of broader scope.

Perl is great at providing mechanisms for lexical scoping: file-based scope, package scope, block scope, subroutine scope, as well as other mechanisms such as do{...}; and eval. It can be a tricky maze to wander at first, but definately flexible.

Perl programmers are lucky in that they can decide just how complex or simple they want their scoping and modularization to be.