That still works; "<FILENAME>dp198076_424b2-us2342673.htm&nbsp\n",
That is because \b is a word to non-word boundary. & is not a word character. Word characters are the ones that you can use in a Perl variable name. [a-zA-Z0-9_]

So we are back at the same problem, you say that there is a problem, but refuse to show any actual code.
If you are actually parsing an HTML doc, you should be using one of the HTML decoder modules before trying to use regex. I believe that haukex has posted some links on that subject. I think you are well advised to read his post in detail.