I think that is probably the clearest way to do it. Here's a way (which I'm not 100% works 100% of the time) that operates on the original list... but as you can see, it's nowhere near as clear:

sub uniq2 {
  my @out = ();
  my ($a, $lasta);

  for ( my $i = 0; $i < @_; $i++ ) {
    splice @_, $i--, 1 if defined($lasta) && $_[$i] eq $lasta;
    $lasta = $_[$i];
  }
  return @_;
}
[download]

I would stick with something similar to what you have above - it's easy to read, follow and maintain.

Although I'm sure someone else can think of an uber-elegant solution :)