open (MAIL, "|/path/to/sendmail -oi -t") || die "Couldn't open sendmail: $!\n";
print MAIL "From: user\@somedomain.com\n";
print MAIL "To: $recip\n";
print MAIL "Subject: whatever\n";
print MAIL "Content-type: text/html\n\n";
print MAIL qq*html content would go here*;
close(MAIL);