my @list = qw( a b c );
GetOptions ('list=s{,}' => \&list);

print Dumper \@list;

sub list {
    # action at a distance
    # modifies the file scoped @list array
    @list = split /,/, $_[1];
}

##</code><code>##

C:\test>list_test.pl
$VAR1 = [
          'a',
          'b',
          'c'
        ];

##</code><code>##

C:\test>list_test.pl -list d,s,4,f,"test string"
$VAR1 = [
          'd',
          's',
          '4',
          'f',
          'test string'
        ];