...
<br>@ => &#64;
...
<br>. => &#46;
...
encoded @ => @, 
<br>and the string has become => this is an @ AT 
<br>and the string_2 has become => &eacute; &acirc; &auml; &agrave; &aring; &ccedil; &ecirc; &euml; &egrave; &iuml; &icirc; &igrave; &Auml; &aring; &Eacute; &aelig; &AElig; &ocirc; &ouml; &ograve; &ucirc; &ugrave; &yuml; &Ouml; &Uuml; &pound; &yen; P &#131; &aacute; &iacute; &oacute; &uacute; &ntilde; &Ntilde; &ordf; &ordm; &iquest; &not; &not; &frac12; &frac14; &iexcl; @ . , &lt; &gt; [ ] { } - _ ; :