OO - as other have said... 'it depends'. I find the question a little unclear, you have items with attributes...

Car
   Wheels=4
   Doors=4
   Color=Blue
Bike
   Wheels=2
   Color=Red
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my %item = (
  Car => {
   Wheels => 4,
   Doors  => 4,
   Color  => 'Blue',
  },
  Bike => {
   Wheels => 2,
   Color => 'Red'
  },
 );
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so how exactly do you want to use $Item? Do you just want to store the details somewhere? or do you want attribute indexes...

my %item = (
  Car => {
   Wheels => 4,
   Doors  => 4,
   Color  => 'Blue',
  },
  Bike => {
   Wheels => 2,
   Color => 'Red'
  },
  Moped => {
   Wheels => 2,
   Color => 'Blue'
  },
 );

# build an index by attribute to item names...
my %attr;
for my $name ( keys %item ) {
  for my $token ( keys %{$item{$name}} ) {
    $attr{$token}{$item{$name}{$token}} ||= [];
    push @{$attr{$token}{$item{$name}{$token}}}, $name;
  }
}

print "Blue things: @{$attr{Color}{Blue}}\n";
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