my @known = (
  { Attribute => 5 },
  { Attribute => 4 },
  { Attribute => 8 },
  { Attribute => 3 },
  { Attribute => 7 },
  { Attribute => 2 }
);

sub byIndex { $a->{Attribute} <=> $b->{Attribute} }
@known = sort byIndex @known;
my $new_item = { Attribute => 6 };
for (my $x = 0; $x < @known; $x++) {
  if ($new_item->{Attribute} <= $known[$x]->{Attribute}) {
    splice(@known, $x, 1, $new_item, $known[$x]);
    last;
  }
}
print $_->{Attribute}, "\n" foreach (@known);