From MorphOS Library
TS [Rexx] - Starts interactive tracing by setting the external trace flag
Starts interactive tracing by setting the external trace flag, which forces all active ARexx programs into interactive tracing mode. Programs will start producing trace output and will pause after the next statement. This command is useful for regaining control over programs Caught in infinite loops or otherwise misbehaving. The trace flag remains set until cleared by the TE command, so subsequent program invocations will be executed in interactive tracing mode.
See also: TE command.