Comment by cubefox

  padding: 1em;
  padding: if(style(--size: "2xl"): 1em; else: 0.25em);

> Note: Remember to include the else condition. In if()-supporting browsers, if no else value were included and --size was not equal to "2xl", the padding would be set to initial.

This is counterintuitive. You would expect the above falls back to "1em" (from "padding: 1em;") when "else" is not specified. Instead, omitting "else" apparently means "else: initial".