@list = qw (one two three);
%args = ( arg1 => 'string', arg2 => 5, arg3 => \@list );

sub1(%args);

sub sub1 {
   my %args = ( arg1 => 'default',
                arg2 => 0,
                arg3 => undef,
                @_
               );
   print "$_ => $args{$_}\n" for keys %args;
}


##</code><code>##

arg1 => string
arg2 => 5
arg3 => ARRAY(0x1a72f84)