\unexpanded\def\showsample#1%
  {\NC \type{#1}%
   \NC \enabletrackers[typesetters.suspects]#1\disabletrackers[typesetters.spacing]%
   \NC \NR}

\startTEXpage[strut=no,offset=1cm]
    \starttabulate[|||][before=,after=]
        \showsample{foo$x$}
        \showsample{$x$bar}
        \showsample{foo$x$bar}
        \showsample{$f+o+o$:}
        \showsample{;$f+o+o$}
        \showsample{; bar}
        \showsample{foo:bar}
        \showsample{\quote{ foo }}
        \showsample{\quote{bar }}
        \showsample{\quote{ bar}}
        \showsample{(foo )}
        \showsample{\{foo \}}
        \showsample{foo{\bf gnu}bar}
        \showsample{foo$x^2$bar}
        \showsample{foo\nobreakspace bar}
    \stoptabulate
\stopTEXpage
