maybe you should look into threads?
use threads;
my $thr = async{ &download_a_file(); };
&calculate_network_bandwidth() while($thr->is_running());
$thr->join();

[download]
but you might need use threads::shared if there are any shared variables.

In reply to Re: Perl Forking : perform some action until child process dies by rmflow
in thread Perl Forking : perform some action until child process dies by robrt

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