Implement a Simple Stopwatch
Operation Flashpoint scripting language,  174  171 bytes

s=""
#l
t=_time
t=t-t%1
a=t%60
c=(t-a)/60
b=c%60
c=(c-b)/60
d=""
e=d
f=d
?a&lt;10:d=0
?b&lt;10:e=0
?c&lt;10:f=0
s=s+format["%1%2:%3%4:%5%6\n",f,c,e,b,d,a]
hint s
@t+1&lt;_time
goto"l"


In action:





158 bytes, if the previous time is overwritten by the next time:

#l
t=_time
t=t-t%1
a=t%60
c=(t-a)/60
b=c%60
c=(c-b)/60
d=""
e=d
f=d
?a&lt;10:d=0
?b&lt;10:e=0
?c&lt;10:f=0
hint format["%1%2:%3%4:%5%6",f,c,e,b,d,a]
@t+1&lt;_time
goto"l"


Technically, no carriage return is used, so I'm not sure if this version confines to the rules.