Description: replace the hack of using #system sleep seconds
to generate pauses. The advantages over #system sleep are:
1) seconds are nolonger limited by interger
2) the tintin will not hang for SECONDS
3) #purge command make it more flexible to use.
NOTE: #10 {#10 practice;#sleep 3} won't work.
if one wants to do so, can: #alias aa {#10 practice;#sleep 3;aa},
ofcoz in real case shall add variable control for jump out of the loop.
See also: #sleep2, #pause, #purge, #slow