You want the caller() builtin:

my ($package, $filename, $line) = caller;

print "It's there!\n" if defined ${$package}::variable;
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Actually, I'm not sure if you can access the varible like that, but it should get you started.

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I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
-- Schemer

Note: All code is untested, unless otherwise stated