use CGI qw(param header);

print header;
if (param('form_submitted') {
   # process form and print results/errors, maybe reprint form
} else {
   # print form
}

##</code><code>##

my $q = CGI->new;
my @CGIValues = values %{$q->Vars};

##</code><code>##

my %param = $q->Vars;   #update: typo (was %q->Vars) thanks BUU