my creates variables only visible to the current scope, and the closures or blocks defined within it. A my variable is not available to anyone outside the scope, or anything called from within the scope, which was not declared inside it (and even so, that gets tricky).

Example:

my $var1;
$_ = '';
FOO: {
    my $var2;
    BAR: {
        my $var3;
        local $_ = 'bar set it';
        &foo();
    }
    GORCH: {
        my $var4;
    }
}

sub foo {
    my $var5;
    print "$_\n";
}
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Every scope in the above code can see $var1, because they were all declared under the main scope, in which $var1 was created. However, the main scope, and sub foo cannot see any variables declared within FOO: {}, and FOO: {} cannot see $var5, which was declared in sub foo. Furthermore, BAR: {} AND GORCH: {} can see everything except each other's private variables, and sub foo's $var5. sub foo, even when called from FOO: {}, BAR: {}, or GORCH: {} cannot see their private (my) variables. It can see local versions of global (our, $_ sorts) variables though - sub foo, called from bar will print "bar set it".

You may also notice, if you use Data::Dumper; print Dumper \%::; that any files you do are also assigned a package, starting with "_<", and then the relative path. You may be able to use those. my experiments have been unsuccessful, but they weren't very thorough either.

Update: I forgot to mention that my and local both create new copies, and new variables, leaving anything with the same name on an outer scope untouched. Also fixed HTML entity.

-nuffin
zz zZ Z Z #!perl