DarkWarning

From hugolib.h:

MovePlayer calls DarkWarning when there is no light source in the new location; replace it with a new DarkWarning routine for a more elaborate response, such as the possible demise of the player

Really, I think that says it best.

The code

routine DarkWarning
{
    print CThe(player); " stumble"; MatchSubject(player); \
        " around in the dark."
}