You mention that you never see the results of your commands. If the module you are using does not have a method to help with this, e.g.

my $error = $self->message();
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or something similar. You could, for development and testing purposes, use something like

$result = qx(mkdir $path);
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To view results.

eval would also provide information if there are problems:

eval{$self->sys('cmd /C mkdir', '-p', "$self->{tmp}/attach")};
if ($@){
   print "$@\n";
}
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