I have been learning Regex (while implementing it in python) the past couple days and haven't figured out how to solve this problem.

I have text in this format:

```
FOO1 = BAR2 AND Var1
Gene3 = Gene4 >= 3
Kinase = MATH OR NOT Science
BOOP = 3

```

I would like to identify each variable name (e.g. FOO1, BAR2, BOOP) and ignore any of the logical operators (e.g AND, OR, NOT)

Here is my attempt to a solution: `(?!AND)(?!OR)(?!NOT)([a-zA-Z0-9]+)`

I am having trouble telling the look-behinds to recognize AND, OR, NOT as words rather than a set of individual characters. 

Any help would be appreciated . Thanks in advance!