Your system call is waiting for input from stdin. You could call 'touch' instead, but how about a pure perl solution?

{
    my $fh;
    open $fh, '>', "/path/to/${num}.bat" or die $!;
}
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You are likely to want a more economical representation of your counter, sooner or later. You should think about flock when you design it.

After Compline,
Zaxo