Using a Logical Expression (LE) , this command lets you select the execution of a set of commands (it can be just one)
according to the logical result of the expression LE.
Symbolically: If LE to be true, then execute commands.
Optionally, a else can be used, that is, if the
logical expression results false, a second set of commands will be executed.
Symbolically:
IF LE to be true, then execute true_commands, else execute false_commands.