I think this is the closest to a "best solution" compared to some the others listed. Define a callback handler for your options such as:

my $flag, @args;
my %more = ( x => 2, y => 1, z => 0 );

GetOptions(
   'x=s' => \&parse_opt,
   'y=s' => \&parse_opt,
   'z=s' => \&parse_opt,
);

sub parse_opt {
   my ($opt, $val) = @_;

   # splice additional args off @ARGV based on how many I expect
   push @args, $val, splice @ARGV, 0, $more{$opt}, ();
}
[download]

Of course, all of this is going to depend on what you want to do with things later and on whether then number of params that -x and -y take varies, etc.