To make sure that never several Karas work on the same block of cloverleafs, the fields of all leafs of all blocks are monitor fields.
First, the Karas have to find a block of cloverleafs (state "search"). If a Kara finds a block, he walks to the end of the block (state "to the end"), replaces the cloverleafs with his own (state "replace") and leaves the cloverleaf block.
Attention: Because the monitor fields are part of the solution, the worlds have to be adjusted (i.e. the monitor fields have to be added) before the program can be started!