It's meant to work for ant build files, which outputs the [javac] lines, but it'll also pickup generic file:line combinations, from grep for instance.
set efm= \\ %#[javac]\ %#%f:%l:%c:%*\\d:%*\\d:\ %t%[%^:]%#:%m, \%A\ %#[javac]\ %f:%l:\ %m, \%-Z\ %#[javac]\ %p^, \%-C\ %#[javac]\ symbol\ %#:\ %m, \%-C%.%#, \%A%f:%l:\ %m, \%-Z%p^, \%f:%l
