my $thing = $cgi->param('action');

my %actions = (
  login => [ \&login ],
  main => [ \&view_page, 'front' ],
  index => [ \&view_page, 'index' ],
  unknown => [ sub { die "unknown action '$thing'" } ],
);

my ($func,@args) = @{ $actions{$thing} or $actions{unknown} };

$func->(@args);