%%% Scary \<space>

In pure \TeX\

\beginverbatim
\show\
\show\ %
\endverbatim

gives the following log on Hans's machine

\beginverbatim
> \
=macro:
->\ .
l.1 \show\

?
> \ =\ .
l.2 \show \
			%
?
 )
No pages of output.
\endverbatim

and on Taco's machine gives:

\beginverbatim
> \^^M=macro:
->\ .
l.1 \show\

?
> \ =\ .
l.2 \show \
			%
?
 )
No pages of output.
\endverbatim

The visualization of a \verb'^^M' depends of the platform but since
there's definitely a newline involved we need to take care of it.
When parsing the input the following happens (this is mentioned in
one of the dangerous bends in the \TeX{}book):

\beginverbatim
\let\x\ <newline> => \let\x\<endlinechar>
\endverbatim

This means that when you want to store the meaning of this
primitive, you need to make sure that \TeX\ explicitly sees a
space instead of a newline. So we get:

\beginverbatim
\let\normalspaceprimitive=\ % space-comment is really needed
\endverbatim

In Con\TeX{}t this is used for:

\beginverbatim
\unexpanded\def\ {\mathortext\normalspaceprimitive{\dontleavehmode\space}}
\endverbatim

If you don't use the explicit space a simple \verb'$\ $'
will execute \verb'\^^M'. In Plain \TeX\ (and in Con\TeX{}t) we have:

\beginverbatim
\def\^^M{\ } % control <return> = control <space>
\endverbatim

So this will result in a loop.
