EReg matches with <code>by</code>.</p>
<p>If <code>this</code> EReg does not match any substring, the result is <code>s</code>.</p>
<p>By default, this method replaces only the first matched substring. If
the global g modifier is in place, all matched substrings are replaced.</p>
<p>If <code>by</code> contains <code>$1</code> to <code>$9</code>, the digit corresponds to number of a
matched sub-group and its value is used instead. If no such sub-group
exists, the replacement is unspecified. The string <code>