\futurenonspacelet

The \futurelet primitive allows you to look at the next token from the input. Sometimes, though, you want to look ahead ignoring any spaces. This is what \futurenonspacelet does. It is otherwise the same as \futurelet: you give it two control sequences as arguments, and it assigns the next nonspace token to the first, and then expands the second. For example:

\futurenonspacelet\temp\finishup
\def\finishup{\ifx\temp ...}