>I invented a freakfest of a conlang a few years back that included both a
>linguolabial trill and a linguolabial click.  It had a full series of
>and clicks/pops from the lips to the glottis.  It used whistles for vowels.
>It also featured a "pro-verb" and forbade transitive verbs.  Like I said --
>a freakfest.

A pro-verb?  Like the following:?

He fell off the cliff.
He2 (proverb)-ed too.

where the proverb essentially acts like the English 'do', and absorbs
whatever arguments are overwritten, or like:

He ate pizza.
She (proverb)-ed gummybears.

where the proverb is just a verb?

In either case, what a brilliantly useful idea!
How miraculous!  A hollow verb!  (I'm being excitable.  Pardon.)

On pro-forms:
What other pro-things are there?  Pronouns, of course, are all over the
place.  IMO this is possible because a noun tends to be used repeatedly in
a discourse, and so methods are devised to avoid that.  On the other hand,
verbs are usually unrepeated for reasonable periods, and so when a proverb
is used it's going to be either in a poetic context or such that the
antecedent's been forgotten, or possibly in a me-too construction.
When a pro-device is used, how does one find the antecedent?  Is it always
the nearest convenient thing, perhaps at the same level of clause nesting,