Uhm, i grepped through parts of my codebase and there is this little gem:

system "aplay /home/cavac/src/pagecamel_dsky/masteralarm.wav &";

Turns out, playing sound on a Raspberry Pi 2(!) is hard, especially from Perl.

And yes, i have seen stuff like OP's code before. Many times. Many, many, times. Unfortunately. At least here on PM this is something that classes under "needs rewrite". I also develop Arduino stuff, and there a source code in that kind of quality would probably class as "made by an expert"...