external-variable-font-face.css

@font-face {
  --a: MyTestFontName;
  font-family: var(--a);
  src: url(/fonts/Ahem.ttf);
}
@font-face {
  font-family: MyTestFontName2;
  src: url(/fonts/Ahem.ttf);
}
#a {
  font-family: MyTestFontName, serif;
}
#b {
  font-family: MyTestFontName2, serif;
}