our @array = 'a' .. 'e';
our @figure_out = 'd' .. 'g';

{
   my $index = 0;
   my %h = map {$_=>$index++} @array;
   while( my($k,$v) = each %h ){

        my $n = shift @figure_out or next;
        $h{$n} = $index++ unless exists $h{$n};
  }

  @array = sort {$h{$a}<=>$h{$b}} keys %h;
}
[download]

That may work in special cases, but `perldoc -f each` tells us not to change a hash while iterating over it, so we end up doing it like that:

{
   my @new = ();
   my $in = sub {
     for(@array,@new){ return 1 if $_ eq $_[0] } return 0
   };
   local $_;
   while( @array ){
      $_ = shift @array;

      #this is of course pseufo for really figuring out
      # a new value
      my $new = shift @figure_out or next;

      $in->($new) or
             push @array,$new;

   } continue {
      push @new,$_
   }

   @array = @new;
}
[download]

An that works.