It should be //echo -s $len($!space) <-> $len($!chr(32))
Kelder and Riamus2's point was that the $space alias definition you suggest acually returns nothing, not even a space.
All that echo command of yours does is return how long the texts "$space" and "$chr(32)" are in characters.
If you actually tried your code before posting it you might actually find that it doesn't work.
Just to spell it out for the blindingly dense: "alias space { return $chr(32) }" does
not return a space, it returns nothing, $null, nada.