$scheme = $cookies{'skin'}
        ? ( ( param( 'scheme' )
          and param( 'scheme' ) =~ /^\w{1,6}$/ )
            ? param( 'scheme' )
            : $cookies{'skin'}->value )
        : ( ( param( 'scheme' )
          and param( 'scheme' ) =~ /^\w{1,6}$/ )
            ? param( 'scheme' )
            : 'default' );


##</code><code>##

use strict;
use warnings;

sub ttw {
  my( $cookie, $param ) = @_;
  my $str = '(' . (defined $cookie ? $cookie : 'undef');
  $str   .= ',' . (defined $param  ? $param  : 'undef') . "):\t";
  $str .= $cookie ||= $param && $param =~ /^\w{1,6}$/ ? $param : 'default';
  $str .= "\n";
  return $str;
}

sub ttd {
  my( $cookie, $param ) = @_;
  my $str = '(' . (defined $cookie ? $cookie : 'undef');
  $str   .= ',' . (defined $param  ? $param  : 'undef') . "):\t";
  $str .= $cookie ||= $param && $param =~ /^\d{1,2}$/ ? $param : 5;
  $str .= "\n";
  return $str;
}

print ttw( 'yellow', 'blue' );
print ttw( 'green', undef );
print ttw( undef, 'teal' );
print ttw( undef, 'chartreuse' );
print ttw( undef, undef );

print ttd( undef, undef );
print ttd( 4, undef);
print ttd( 444, undef);
print ttd( undef, 3);
print ttd( undef, 333);
print ttd( 6, 7);


##</code><code>##

(yellow,blue):  yellow
(green,undef):  green
(undef,teal):   teal
(undef,chartreuse):     default
(undef,undef):  default
(undef,undef):  5
(4,undef):      4
(444,undef):    444
(undef,3):      3
(undef,333):    5
(6,7):  6


##</code><code>##

$scheme = $cookies{'skin'} ||= param( 'scheme' )
                            && param( 'scheme' ) =~ /^\w{1,6$/
                             ? param( 'scheme' )
                             : 'default';


##</code><code>##

$scheme = $cookies{'skin'}->value ||= param( 'scheme' )
                                   && param( 'scheme' ) =~ /^\w{1,6$/
                                    ? param( 'scheme' )
                                    : 'default';


##</code><code>##

$/  =  q#(\w)#  ;  sub  sig { print scalar reverse  join  ' ',  @_  }  sig
map { s$\$/\$/$\$2\$1$g && $_ } split( ' ', ",erckha rlPe erthnoa stJu" );