$1 is tex, $2 is closing, $3 is tex
$1 is opening, $2 is tex
$1 is opening, $2 is tex, $3 is closing, $4 is label
TODO: Scope these properly
This adds support for eqref
TODO: Properly scope all these regexps Everything goes; takes care of escaping the “$” inside the expression
This adds support for ref