my @ref = qw(Red Green Yellow);
my @data = qw(Yellow Black Yellow Red White Yellow);
for my $search (@ref)
{
  my @found;
  for my $index (0..$#data)
  {
    if ($data[$index] eq $search)
    {
      push @found, $index;
    }
  }
  print "$search: [@found]\n";
}

##</code><code>##

Red: [3]
Green: []
Yellow: [0 2 5]