Running a program in the background doesn't suppress STDOUT.

If you just want to suppress the output and not do anything with it you can redirect it to /dev/null:

system("/some/program >/dev/null");
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If you want to capture its output to process it, the easiest way is to use `` quotes:

my $output = `/some/program`;
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If your program has a lot of output that is better captured as it arrives you can use piped open:

open(my $handle, "/some/program|") or die;
while (<$handle>) {
  # do stuff with a line
}
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See also perlopentut and perlipc.