Haskell greedy elem?

Use break:

Prelude> break (==':') "192.168.0.1:5000"
("192.168.0.1",":5000")
Prelude> break (==':') "192.168.0.15"
("192.168.0.15","")

You might like the split package

bash> cabal update && cabal install split
bash> ghci
ghci> import Data.List.Split
ghci> splitOn ":" "192.168.0.1:9000"
["192.168.0.1","9000"]