The IF command makes it possible to execute some commands conditionally. The format of the command is:
IF condition THEN commands [ ELSEIF condition THEN commands ]* [ ELSE commands ] ENDIF
The ELSEIF part is conditional, need not present and there can be many of it in a single IF command. Similarly the ELSE part is also optional but there can only be one ELSE part.
Note that the keyword ELSEIF is a single keyword and it is syntactically incorrect to write "ELSE IF" in two words.
The condition can be any expression that evaluates to a boolean value. There is no automatic conversion from non boolean values to boolean value.