From perlipc

...doing nearly anything in your handler could in theory trigger a memory fault and subsequent core dump.

In your case I would simply do this:

while (1) {
    $self->check_start();
    $self->check_run();

    # Sleep 1/10 second
    select(undef, undef, undef, 0.1);
    1 while (waitpid(-1, &WNOHANG) > 0);
}
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--perlplexer