What happens if you press !T at the command line?
I suspect you are not doing something correctly as AutoCAD always interprets the space as a string if you are using the T in the getstring command.
It works perfectly for me here ... perhaps you are making your variable S local to some code ... it is really hard to guess what could be wrong without a little help from you, other than "it don't work". ... maybe a copyclip from the command line, the code you are trying to put it in, a screen shot, something ... anything ... will be better than nothing.