Hmmm. Consider the following:

use strict;
use warnings;
use Benchmark 'cmpthese';

use constant MAX => 520;

my %contracts = ( 1 .. 2 * MAX );

cmpthese ( -1,
  {
    lookup => \&lookup,
    refit => \&refit,
  }
);

sub lookup {
  for ( keys %contracts )  {
    return if $contracts{$_} == MAX;
  }
}

sub refit {
  for ( keys %contracts )  {
    my $ref = \$contracts{$_};
    return if $$ref == MAX;
  }
}
[download]

Output (on my machine):

         Rate  refit lookup
refit  4263/s     --   -21%
lookup 5407/s    27%     --
[download]