I never realized, but 1.5 supports \ & / regardless of 'Replace forward slashes with backslashes' setting - at least in some areas.
In particular in file paths, where you can use \ or / or \ and / or even \/
c:/out/mmm/gui
c:\out\mmm\gui
c:/out\mmm/gui
c:\/out\/mmm\/gui
(Other areas might present gotcha's, but you can even get away with something weird like: regex:c:\\out/\mmm.)