# ...
open (MAIL, "|/usr/lib/sendmail -oi -t") or die "Can't fork sendmail: $!";
print MAIL <<EOF;
From: requestor@from.foo.net
To: Receiver@to.foo.net
Subject: Requested Calendar Event

EOF
CGI::save_parameters(*MAIL);
close (MAIL) or die "can't close sendmail: $!";
# ...