I’d like to let a blank input make it through to the ‘after reading a command’ stage so that I can intercept it with
if the player's command is "";
… rather than it just going to ‘I beg your pardon?’
My goal is not to print a cute message in response, otherwise I would use a rule for printing a parser error or such as the docs advise. The reason I want to do this is so I can convert a blank input into a repeat of the previously entered command, which is easy to do once we get to ‘after reading a command’.
A caveat is that I am using Unified Glulx Input by Andrew Plotkin, which already contains an edited version of ParserInput. So I was hoping to poke a little modification in there?