elseif IF statement condition.
elseif is used with IF. The statements after the elseif are
executed if the expression is true and all the preceding IF and
elseif expressions are false. An expression is considered true if
the real part has all non-zero elements.

elseif does not need a matching END, while ELSE IF does.

The general form of the IF statement is
IF expression
statements
elseif expression
statements
ELSE
statements
END

See also if, else, end.