The statement looks similar to
try...catch blocks found in many high-level programming languages like C++ and Java. However, in
catch() you can put a condition that will be checked every in-game tick. If this condition becomes true, code in try block will be interrupted and control will be returned to the catch block. This allows you to interrupt your program if something extraordinary happens. For example, you can order the bot to check if an ant is near it’s position and return to base in such case.
There was no information about it in CBOT manual. It was found in one of the documents EPSITEC gave us together with the source code of Colobot.