There are some platform-specific libraries for manipulating keyboard LEDs (like xleds), but the link above is working with hardcoded memory locations. It'll work on any i386 platform, regardless of OS. Now, getting to work on a different architecture is a different matter . . .

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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