Make punctuation active characters and map them to the \nogloss macro (XeTeX)

Question

This is a follow-up to this answer and comment. Does anyone have an idea how to automate the \nogloss macro so that I don't have to label every punctuation mark (or at least ! ? " , .) with it?

EDIT: Thanks to @Alan Munn, I now realize that I'm looking for a XeTeX-compatible solution.

MWE:

\documentclass{book}        
\usepackage{expex}    
\lingset{glwordalign=center}

\begin{document}    
\exdisplay
\begingl
  \gla \nogloss{``} @ aaaaa aaaaaaa @ \nogloss{!''} aaaa aaaa aaaa @ \nogloss{\ldots} //      
  \glb bbbbb bbbbbbb bbbb bbbb bbbb //      
  \glc ccccc ccccccc cccc cccc cccc //      
\endgl
\xe    
\end{document}

EDIT: To clarify, I want my input to be like the MWE below but for the automation to yield the MWE above, or at least the output of what the above code would yield.

\documentclass{book}        
\usepackage{expex}    
\lingset{glwordalign=center}

\begin{document}    
\exdisplay
\begingl
  \gla "aaaaa aaaaaaa!" aaaa aaaa aaaa... //      
  \glb bbbbb bbbbbbb bbbb bbbb bbbb //      
  \glc ccccc ccccccc cccc cccc cccc //      
\endgl
\xe    
\end{document}

Answer 1

Using the technique explained in Mico's answer here:

• Automatically replace environment align by equation+aligned combination

We can do the same thing for your cases. This requires compilation with LuaLaTeX.

Note: This answer was added before we discovered that a XeLaTeX solution was required, but I will leave it here since many (but not all) XeLaTeX documents can be compiled with LuaLaTeX as well.

This is lightly tested. The function checks for opening quotes and trailing punctuation followed by a space, so it should work as intended if your input looks like that. For example, it won't include word internal punctuation marks like a colon marking vowel length.

% !TEX TS-program = lualatex
\documentclass{article}
\usepackage{expex}
\lingset{glwordalign=center}

\usepackage{luacode}
\begin{luacode*}

function replace_punc ( buff )
   if string.find ( buff , "\\gla" ) then
      buff = string.gsub ( buff , " (``)" ,
             "\\nogloss{%1} @ " )
      buff = string.gsub ( buff, "([:.,;'!?]+)( )" ,
          " @ \\nogloss{%1}%2" )

   end
   return ( buff )
end

luatexbase.add_to_callback ( "process_input_buffer", replace_punc, "replace_punc" )
\end{luacode*}


\begin{document}    
\exdisplay
\begingl
  \gla ``aaaaa aaaaaaa!?:!'' aaaa aaaa aaaa. //      
  \glb a bbbbbbb bbbb bbbb bbbb //      
  \glc ccccc ccccccc cccc cccc cccc //      
\endgl
\xe    

\end{document}