Seems like you want to temporarily redirect STDOUT to somewhere else?

You'll find lots of good stuff if you Super Search here for "redirect stdout" or similar.

This is a VERY basic way of doing it, which might get you started:

print "This goes to stdout\n";
{
    local *STDOUT;
    open STDOUT, '>/tmp/myoutput';
    print "This gets redirected\n";
    # more code here that prints stuff to stdout
}
print "Back to normal stdout\n";
[download]

If you really don't need the output of your external.pm then change /tmp/myoutput to /dev/null (if you're on Unix).

Disclaimer: I've never actually used techniques like this in real code, there may be problems/caveats etc. Searching this site should turn up more robust solutions!