code: function checkAtkeyword(i) {
    let l;
  
    // Check that token is `@`:
    if (i >= tokensLength ||
        tokens[i++].type !== TokenType.CommercialAt) return 0;
  
    return (l = checkIdentOrInterpolation(i)) ? l + 1 : 0;
  }
docs: Checks if token is part of an @-word (e.g. `@import`, `@include`).
  
  @param {number} i Token's index number
  @return {number}