= millisec: millisecond timer     include "sys.m";    sys := load Sys Sys->PATH;     millisec: fn(): int; Millisec  returns  the  value of an internal system clock, inmilliseconds.  The actual resolution of the clock is a  prop‐erty  of the underlying system and may be coarser than a mil‐lisecond.  The epoch is arbitrary, so millisec is useful  formeasuring  durations  but  not  absolute time.  If the systemoperates  continuously,  the  millisecond  counter  overflowsevery few months; a reboot resets the epoch. == see ALSOsys-intro(2), sys-sleep(2)