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my @hash = ( 
  .1 => 'url1',
  .2 => 'url2',
...
  .7 => 'url7',
  .9 => 'url9',
);

#define your data:
my @hash = ( 
...

my %hash = ( .1 => 'url1', .2 => 'url2', .5 => 'url5', .9 =>'url9' );
my $fitness = sub { $_ > .4 };
...
  my ($hashr, $fitness) = @_;
  return map { $fitness->($_) keys %$hashr 
}

sub find_good_keys 
{
  my ($hashr, $fitness) = @_;
  return map { $fitness->($_, $hashr ) } keys %$hashr 
}

my $fitness = sub { my ($key, $hashr ) = @_ ;
  return .3 <= $key && . 7 >= $key && $hashr->{$key} =~ m/foo/i ? 1 : 
+0
...
  my ( $hashr, $fitness ) = @_;
  return map { $fitness->( $key, $hashr ) } keys %$hashr;
}