// We can force a travel exclusion by using the "force_exclude"
    // KPROP feature property in vaults. {due}
    if (testbits(env.map(p).property, FPROP_FORCE_EXCLUDE)) 
        return (true);

    if (str == "force_exclude")
        return (FPROP_FORCE_EXCLUDE);

    FPROP_NONE = 0,
    FPROP_SANCTUARY_1 = (1 << 0),
    FPROP_SANCTUARY_2 = (1 << 2),
    FPROP_BLOODY      = (1 << 3),
    FPROP_VAULT       = (1 << 4),
    FPROP_HIGHLIGHT   = (1 << 5)  // Highlight grids on the X map for debugging.

    FPROP_NONE          = 0,
    FPROP_SANCTUARY_1   = (1 << 0),
    FPROP_SANCTUARY_2   = (1 << 2),
    FPROP_BLOODY        = (1 << 3),
    FPROP_VAULT         = (1 << 4),
    FPROP_HIGHLIGHT     = (1 << 5),  // Highlight grids on the X map for debugging.

    FPROP_FORCE_EXCLUDE = (1 << 6)

KPROP:    x = bloody
          KPROP: allows you to assign a specific property to a feature. Like
          KFEAT: and KMONS:, it can be combined with these for the same place-
          holder.
          Available properties are: 
          
          * "bloody": Causes features to appear as though splattered with
             blood. This should be used very, very sparingly!   
          * "force_exclude": Forces a single grid square or feature to be an 
             exclusion in auto-explore and automatic travel. Will be coloured
             red in the overmap.