TinTin++ Mud Client Manual
         IF

Command: #if {conditional} {commands if true}

         The #if command is one of the most powerful commands added since
         TINTIN III. It works similar to an if statement in other languages,
         and is based on the way C handles its conditional statements.
         When an #if command is encountered, the conditional statement is
         evaluated, and if TRUE (any non-zero result) the commands are executed.

         The if statement is only evaluated if it is read, so you must nest
         the if statement inside another statement (most likely an #action
         command). The conditional is evaluated exactly the same as in the
         #math command, only instead of storing the result, the result is used
         to determine whether to execute the commands.

         To handle the case where an if statement is false it can be followed
         by the #else command.

Example: #action {%0 gives you %1 gold coins.} {#if {%1 > 5000} {thank %0}}
         If someone gives you more than 5000 coins, thank them.

Example: #alias {k} {#if {"%0" == ""} {kill $target};#else {kill %0}}

Comment: See '#help math', for more information.

Related: case, default, else, elseif, switch and regexp.