# grep regex to ignore comment at end of line?

I'm trying to grep through a lot of old PowerBASIC source files in search of a variable, but I'm having trouble getting grep to avoid matching references to the variable in the end-of-line comments. For example: ANGLE = 40 ' THIS IS A COMMENT ABOUT ANGLE'S VALUE FOO = 3/ANGLE ' ANGLE CAN APPEAR ON RIGHT SIDE AS WELL DELTA = 35 ' ANGLE AND DELTA AREN'T FRIENDS Initially I was using: # grep "\\bANGLE\\b.*'" SRC_FILE.BAS But -- besides ignoring lines with no comments -- it also prints out lines of code which don't use ANGLE at all (such as the DELTA line). This is because those lines happen to also have a *single* apostrophe (') in their comments (i.e. AREN'T). I thought of piping the output to remove the lines I don't want with: # grep "\\bANGLE\\b" SRC_FILE.BAS | grep -v "'.*\\bANGLE\\b" But unfortunately it also removes the lines of code I do want that just happen to have "ANGLE" in their comments. How do I get grep to match the lines of actual code involving ANGLE and ignore those lines with *only* matches in the comments?