Optional argument of if. It's usually good style to omit the then itself, but can aid clarity when using multi-line expressions. Compare with else.
if {$some_long_and_complex_condition
&& $some_other_condition_making_it_even_longer
} then {
# do the right thing here
} else {
# do the other right thing here
}wdb In my humble opinion, clarity matters always, such that I personally count the usage of then to the list of good style. But, of course, that's my personal taste. I suppose that usage of then does not impact the perfomance.