This line is tripping you up:

open ( LOG, $log ) || warn "  Couldn't open log\n"
    if ($debug);
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It'll only open the file if the $debug flag is true. The if is much higher in precedence than ||. This will work instead:

open( LOG, $log ) or do
{
    warn "    Couldn't open log: $!\n" if $debug;
};
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