I just made a bug for this here:
http://sourceforge.net/tracker/index.php?func=detail&aid=1873180&group_id=45545&atid=443219
"Regular and Backslash expressions should be mutually exclusive.
In the Search dialog, there are two checkboxes:
"Regular expression"
"Allow backslash expressions"
These are two conflicting options, so the checkboxes should be mutually
exclusive. It looks like right now the Regular expression takes precedence
if they are both checked, but you really shouldn't be able to check both
unless you can actually use both.
I propose that if you check one of these checkboxes, the other is
automatically unchecked. This would solve confusion, and more accurately
reflect how they really operate."