IF condition THEN statement1 [ELSE statement2]
Statement1 and statement2 can be any valid statement as described at the beginning of the section on statements.
The IF statement is used to make a decision based upon some condition. The action of this statement is as follows:
evaluate the condition
if the result of the condition is nonzero (true),
if the result of the condition is zero (false),
do statement2 if specified.
IF last_pdate LT $todays_date-30 THEN