Perfection?

  function re(first, ...args) {
    let flags = first;
    function tag(template, ...subs) {
      const parts = [];
      const numSubs = subs.length;
      for (let i = 0; i < numSubs; i++) {
        parts.push(template.raw[i]);
        const subst = subs[i] instanceof RegExp ? subs[i].source :
            subs[i].replace(/[\/\\^$*+?.()|[\]{}]/g, '\\$&');
        parts.push(subst);
      }
      parts.push(template.raw[numSubs]);
      return RegExp(parts.join(''), flags);
    }
    if (typeof first === 'string') {
      return tag;
    } else {
      flags = void 0;  // Should this be '' ?
      return tag(first, ...args);
    }
  }
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Perfection?

```js
  function re(first, ...args) {
    let flags = first;
    function tag(template, ...subs) {
      const parts = [];
      const numSubs = subs.length;
      for (let i = 0; i < numSubs; i++) {
        parts.push(template.raw[i]);
        const subst = subs[i] instanceof RegExp ? subs[i].source :
            subs[i].replace(/[\/\\^$*+?.()|[\]{}]/g, '\\$&');
        parts.push(subst);
      }
      parts.push(template.raw[numSubs]);
      return RegExp(parts.join(''), flags);
    }
    if (typeof first === 'string') {
      return tag;
    } else {
      flags = void 0;  // Should this be '' ?
      return tag(first, ...args);
    }
  }
```