SIGUSR1 causes the process to break out of a sleep.

Note that the C code:

    for(;;) {
        sleep(1);
    }
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is not semantically equivalent to the Perl code:

    while(sleep(1)) {

    }
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Instead, in Perl, try either of the following for the same effect:

• for (;;) { sleep(1) }
• while (1) { sleep(1) }
• sleep(1) while 1;