As others have stated, the hash is the way to go here.
If you are concerned about order, there are modules that keep care of that:

• Tie::IxHash (pure perl)
• Tie-Hash-Indexed (similar to Tie::IxHash, but faster. written in c)

There is also Tie::Array::Unique which sounds promising, but itīs version 0.01 and I never used it.