[code=perl]
my $action = param('action') || undef;
$action    = defined $action  ? $action =~ s/[^a-zA-Z0-9_-]//g
           : 'home'
           ;

my $action = defined param('action') ? param('action') =~ s/[^a-zA-Z0-9_-]//g
           : 'home'
           ;