# 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.