my $r = shift;  # or $r = Apache->request
my %params = $r->method eq 'POST' ? $r->content : $r->args;

Also take a look at Apache::Request, which has the same API as CGI.pm for extracting and setting request parameters but is significantly faster, since it's implemented in C.

A.7. Sending Cookies in REDIRECT Responses		A.9. Sending Email from mod_perl