# Run executable @system command, reporting name as $name If there 
# is an upload limit, we run through trickle(1) to limit bandwidth.
sub _ext_cmd {
    my ($name, @system) = @_;
    
    if ($o{general}{upload}) {
        @system = ($o{general}{trickle},
                   $o{general}{trickled} ? () : '-s',
             -u => $o{general}{upload}, '|', @system);
    }        
    say "Running name=$name, @system";
    # system { $system[0] } @system[1..$#system]; # Obviously nope.
    say "\$?=$?";
}
##</code><code>##

# Excerpt of %o options hash:
%o = (
    general => {
        upload   => '256', # KBps
        trickle  => '/bin/trickle',
        trickled => undef, # True if trickled is installed
    },
);

# Example usage:
_ext_cmd(display_name => qw!/bin/duplicity /path/to/src /path/to/dest!);
# ... but you could probably test it just fine with echo or /bin/cat.