I have a paragraph that needs to be converted into xml paragraph includes spaces (&nbsp;) and simple ampersand (&) and ofcourse <br> tags. Here is my regex

$str =~ s/br\>/br\/\>/g;
$str =~ s/nbsp/#160/g;
$str =~ s/&/&amp\;/g;

<br> tags are easily manipulated into <br/> but for &nbsp it puts &amp;#160; I know that its basically first changing nbsp to #160; and than the next line goest and adds &amp; to my ampersand. How do I approach this problem so for all & cases it puts &amp; and for all &nbsp cases it puts   Please help.