$pdf_mode = 4;            # lualatex
$bibtex_use = 2;          # biber
$out_dir = out;
$clean_ext .= ' %R.run.xml %R.bbl %R.bcf %R-blx.bib';

# Never stop for a prompt: a failing listing would otherwise loop forever.
$lualatex = 'lualatex -interaction=nonstopmode -halt-on-error %O %S';