_msgid_       The message identifier of the current thread.

_age_       The "depth" of the message in recursive calls.

_ticks_       The number of ticks used by the thread so far.

_player_       The player who typed the command that initiated this thread.

_on_       The object on which the method which is executing is defined.

_caller_       The object which called this method.

_args_       The arguments to this method, when called.

_methodname_       The name of the currently-executing method.

_blocked_on_       A numeric identifier, indicating the state of the
                   currently-executing thread.

_timer_       A numeric value, indicating the time at which the current
              thread will resume, or expire (depending on state).