Reg Expression Q: How to revere match literal string?

[lierduh]

I want to search for line breaks, but excluding certain ones. eg.

I want to search for

"abc\r\nABC" or "<abc>\r\n<ABC>"...

...but I do not want to include

"<ul>\r\n<li>" or "</li>\r\n<li>"

So what I need is to reverse match strings. A '^' in a character class only negates a single character, not a string. Any idea for me how to achieve this? Thanks. I could have some mental block if this turns out to be something very simple.