Dynamically creating a hash for keys()

Can anyone help me to understand why this code refuses to compile?  
Even better, can anyone help fix it :)

     %hash = qw( fred filntstone barney rubble tom delong );
     print( keys( reverse( %hash ) ) );

The error message...

     Type of arg 1 to keys must be hash (not reverse) at ./killme.pl 
line 4, near ") ) "

... was pretty confusing since it implies that "reverse" is a type?!

I tried making an anonymous hash as follows...

     print( keys( %{ reverse( %hash ) } ) );

... but got no results at all.

Help!