Mire some land, as if it was hit by a particle. Unlike using SetMire, MireLand will mire the closest connected cell if the target cell is already mired in the same colour. If you need to know if there was mire laid down or not, use MireLand2. (Mire may not be created if the target landmass is already fully mired.)

Unknown effect when used on metallic land.

    # Fully mire a landmass in red (well, up to 10000 cells in size).
    once
        10000 0 do
            CurrentCoords 1 MireLand
        loop
    endonce