sub withNames{ local %_ = @_; ++$_{$_} for keys %_; };;

sub sansNames{ ++$_ for @_; };;

cmpthese -1,{a=>q[ withNames( 1 .. $_*2 ) for 1..5 ], b=>q[ sansNames( 1..$_ ) for 1 .. 5 ] };;
      Rate    a    b
a  32135/s   -- -75%
b 127549/s 297%   --