Function false_loop 

pub fn false_loop<ET: EngineTypes>(
    engine: &mut EngineReferences<'_, ET>,
    idx: usize,
    allowelse: bool,
    skipelse: bool,
) -> TeXResult<(), ET>

What to do on a false conditional - skips Tokens until the next \else (if allowelse is true) or \fi If skipelse is false, precisely one \else is skipped as well (this happens in \ifcase when the appropriate case is already done, so the corresponding \else should be skipped).