You need a blank line between the headers and the body.

Also, "fuction(arguments);" won't interpolate the result you want.

You'd probably want something like this, assuming your sendmail arguments are correct:

open(SENDMAIL, "|/usr/lib/sendmail -oi -t -odq")
  || die "Cannot for mail: $!";

# function?  You'll want to specify real arguments, of course
my $body=fuction(arguments);

# Don't forget the Date: and Subject: headers

print SENDMAIL << "EOF";
From: me\@abc.com
To: you\@xyz.com

$body
EOF

close(SENDMAIL);
[download]

I prefer using Net::SMTP myself, or MIME::Lite. MIME::Lite is especially easy to use.
--
Mike