Your first use to generate scalar methods is an OK use of symbolic references, because the way to create a named subroutine without using symbolic references is far more unwieldly:

$::My::Package::{$attributeScalar} = sub {...};
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But why aren't you using Class::Accessor or any of the other modules which create such accessors for you?

Using symbolic references in dispatch tables is convenient until you need to think about which subroutines are to be called dynamically and which not. Using hard references in a hash is self-documenting and more secure, and allows for renaming of the exported name:

use vars qw(%user_methods);
%user_methods = (
    handle_foo => \&handle_foo,
    handle_bar => \&handle_bar,
    handle_baz => \&do_handle_baz,
);

...
sub handle {
    my $data = shift;
    for my $filter (@_) {
        if (exists $user_methods{ $filter }) {
            $data = $user_methods{ $filter }->($data);
        } else {
            die "Unknown filter method '$filter'";
        };
    };
};
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Your third test will always succeed - you can always set global package variables. Also, I would ditch the C-style for loop in favour of:

for my $i (0..1) {
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