Why writing your own "decoder"? You could just borrow the decoder from CGI. I quickly wrote the following example to show how to decode the named parameters (nicely).

use strict;
use Data::Dumper;
use CGI::Util qw/rearrange/;

# when called as a method
__PACKAGE__->test( -option1=>'a', -option3=>'c' );

# called as a normal function
test( -option1=>'a', -option3=>'c', -option2=>'b' );

# called with unnamed parameters
test( 'a', 'b', 'c' );


# our little test method/function
sub test
{
  my($self,@p) = self_or_default(@_);
  my($option1,$option2,$option3,@other) =
        rearrange([qw/ OPTION1 OPTION2 OPTION3 /],@p);

  print "\$option1=$option1\n\$option2=$option2\n\$option3=$option3\n\
+n";
}


# borrowed from CGI.pm with minor modification  ;-)
sub self_or_default {
  my $class = __PACKAGE__; # name of the class, set to main for testin
+g
  return @_ if defined($_[0]) && (!ref($_[0])) && ($_[0] eq $class);

  my $Q = undef;
  unless (defined($_[0]) &&
         (ref($_[0]) eq $class || UNIVERSAL::isa($_[0], $class)))
  {
    $Q = {};
    bless $Q, __PACKAGE__;
    unshift(@_,$Q);
  }
  return wantarray ? @_ : $Q;
}
[download]

And the output is just what we expected -

$option1=a
$option2=
$option3=c

$option1=a
$option2=b
$option3=c

$option1=a
$option2=b
$option3=c
[download]