In your stopsmc() function you are calling system. On Microsoft Windows only, system has an additional feature. It has an optional first parameter which, if non-zero, runs the job asynchronously in the background - a bit like appending '&' to a command on UNIX. For example:

my $pid = system(1, 'background.exe');
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In this case system returns the process id of the child. This is documented in perlport - probably not the first place you would look for it!

You have a function called timedelay() and you don't say why you need that. Maybe that could be utilised as a timeout?