How to forward email to a perl script on Linux

I would like all mail sent to a particular alias on a Linux machine to be processed by a perl script but sendmail is giving me a "Service unavailable" error and I don't understand what I'm missing.

I created my handle_email.pl script (right now, this just prints its parameters to /tmp/email.txt) and added a symbolic link to it in /etc/smrsh.

Then I added this to /etc/aliases:

mailtest: |handle_email.pl

and ran newaliases afterwards. Note that I've also tried mailtest: |/etc/smrsh/handle_email.pl which gave the same results. I've also tried copying the actual script into /etc/smrsh rather than a link, same results again.

When I send mail to the mailtest alias, the file in /tmp never gets created, and I get this in /var/log/maillog:

Nov  1 14:43:59 localhost sendmail[24839]: qA1IhwHm024839: from=<xxx@xxx>, size=284, class=0, nrcpts=1, msgid=<201211011843.qA1IhwHm024839@localhost.localdomain>, proto=ESMTP, daemon=MTA, relay=[10.7.160.180]
Nov  1 14:43:59 localhost smrsh: uid 8: attempt to use "handle_email.pl"
Nov  1 14:43:59 localhost sendmail[24850]: qA1IhwHm024839: to=|handle_email.pl, ctladdr=<mailtest@xxx> (8/0), delay=00:00:00, xdelay=00:00:00, mailer=prog, pri=30570, dsn=5.0.0, stat=Service unavailable
Nov  1 14:43:59 localhost sendmail[24850]: qA1IhwHm024839: qA1IhxHm024850: DSN: Service unavailable
Nov  1 14:44:00 localhost sendmail[24850]: qA1IhxHm024850: to=<xxx@xxx>, delay=00:00:01, xdelay=00:00:01, mailer=esmtp, pri=31594, relay=sy-int-mx.xxx. [<IP addr>], dsn=2.0.0, stat=Sent (qA1Ii4127508 Message accepted for delivery)

I get an email message describing the failure, which says:

The original message was received at Thu, 1 Nov 2012 14:58:16 -0400
from [<ip address>]

   ----- The following addresses had permanent fatal errors -----
|/etc/smrsh/handle_email.pl
    (reason: Service unavailable)
    (expanded from: <mailtest@xxx>)

   ----- Transcript of session follows -----
smrsh: "handle_email.pl" not available for sendmail programs
554 5.0.0 Service unavailable

Why will smrsh not execute my script?

Update: Answering questions in comments.

I've copied the script to /etc/smrsh and removed the link. The file permissions are 0700 (also tried 0755) and the first line is #!/usr/local/bin/perl which is correct. There is only one file in /etc/smrsh. The ls -l output:

[main:g:64] xxx:/etc/smrsh# ls -l
total 4
-rwx------. 1 root root 281 Nov  1 16:35 handle_email.pl