If tac is a tactic, TRYALL tac is a list-tactic which,
when applied to a list of goals,
applies the tactic tac to each goal for which it succeeds.
When tac fails on a goal, TRYALL tac has no effect on that goal.
FAILURE
The application of TRYALL to a tactic never fails.
The resulting list-tactic never fails.
EXAMPLE
Where tac1 and tac2 are tactics,
tac1 THEN_LT TRYALL tac2 is equivalent to tac1 THEN TRY tac2