The splat operator in Ruby, Groovy and Perl allows
you to switch between parameters and arrays:
it splits a list in a series of parameters,
or collects a series of parameters to fill an array.

The split mode turns an array into multiple-arguments:

>> duck, cow, pig = *["quack","mooh","oing"]
=> ["quack","mooh","oing"]

The collect mode turns multiple-arguments in an array:

>> *farm = duck, cow, pig
=> ["quack","mooh","oing"]

The splat operator can be used in a case statement :

WILD = ['lion','gnu']
TAME = ['cat','cow']

case animal
 when *WILD
 when *TAME

And it can be used to convert a hash into an array:

>> a = *{:a=>1,:b=>2}
=> [[:a,1],[:b,2]]
>> Hash[*a.flatten]
=> {:a=>1,:b=>2}