Also, before you start just trying things to see if they work, you might try to understand what the comma operator is doing, and how you are building a string. Try to convince yourself that:
this is a test
is the same as
this , #SPC , is , #SPC , a , #SPC , test
and that
this is a test
is NOT the same as
this is , #SPC , a test.
(EUO speaking that is.)