Re: [Haskell-cafe] How to understand `|` in this code snippet ?

On Sat, Feb 27, 2010 at 5:07 PM, zaxis wrote:

xxxMain = do    timeout <- getEnv "xxx_TIMEOUT"    case timeout of        Just str | [(t, _)] <- reads str -> do            addTimeout t (hPutStrLn stderr "*** TIMEOUT" >> _exit 1)            return ()        _ -> return () .......

What does the `|` mean in "Just str | [(t, _)] <- reads str" ? Is it a logical `or` ?

It's part of a case expression, see http://www.haskell.org/onlinereport/exps.html#sect3.13 lee