{Recollections of a spurious space catcher} {Enrico Gregorio} {Programming in \TeX\ has always posed several hurdles towards pure and error free programs. One of the most often seen errors is related to spurious spaces, missing \code\%s at end of lines that cause head scratching to the user of the macros. But there's also the opposite problem of missing spaces, which is even subtler, because it can cause unscrutable errors far away. Other typical errors will be presented, related to order of expansion or misused conditionals. We'll do an {\it excursus\/} through these issues, but this is mostly an excuse for presenting the new paradigm of \TeX\ programming provided by \pkg{expl3}, now not restricted to \LaTeX\ only. Programming \TeX\ with \pkg{expl3} can be easy or difficult, depending on the approach to it. Some important examples will be presented, along with solutions for generic tasks which have always taken many lines of code, with duplication of efforts, or short and nice, but unscrutable, code.}