You are not, contrary to your belief, launching a background process.

If you call system with a list of arguments it is not interpreted by the shell, instead Perl launches the appropriate process with the list of arguments passed in directly (so shell metacharacters are not interpreted as such).

You want to do something more like:

system(join " ", @command, "&");
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As for your test from which you believed that the process was backgrounded, under Unix if you create a child process and then kill the parent, the child process just continues and is reparented. So your test for whether you created a background process only really tested to show that you created a process.