on goto -- jump to one of many goto-targets
on a goto foo,bar,baz
The on goto statement uses its numeric argument (the one between on and goto to select an element from the list of labels, which follows after the goto-keyword: If the number is 1, the execution continues at the first label; if the number is 2, at the second, and so on. if the number is zero or less, the program continues at the position of the first label; if the number is larger than the total count of labels, the execution continues at the position of the last label; i.e. the first and last label in the list constitute some kind of fallback-slot.
Note, that (unlike the goto-command) the on goto-command can no longer be considered state of the art; people may (not me!) even start to mock you, if you use it.
print "Please Select one of these choices: "
print " 1 -- show time"
print " 2 -- show date"
print " 3 -- exit"
input "Your choice " a
on a goto over,show_time,show_date,terminate,over
Note, how invalid input (a number less than 1, or larger than 3) is automatically detected; in such a case the question is simply issued again.
goto, on gosub