pug.renderFile('input.pug', {
  plugins: [{
    lex: {
      blank(lexer) {
        if (lexer.input[0] === '~') {
          lexer.tokens.push(lexer.tok('text', 'twiddle-dee-dee'));
          lexer.consume(1);
          lexer.incrementColumn(1);
          return true;
        }
      }
    }
  }]
});