In Vim, how do I match on "=" but not on "=="?

I've tried a number of different search patterns: - `[^=]=[^=]` works but only if = is not at the beginning/end and it also matches the sandwiching characters - `=\@!==\@!` seems like it should work because \@! matches nothing but requires a match, but it doesn't (see :help pattern-overview) - `[^=]\@==[^=]\@=` also doesn't but seems like it should Suggestions?