In /etc/httpd.conf:

server "" {
        listen on * port 80
        root "/htdocs/perl"
        location "*.pl" {  
        location "/.well-known/acme-challenge/*" {
                root "/acme"
                request strip 2

To figure out what files need to be copied into the chroot:

$ ldd /usr/bin/perl /usr/bin/perl:

        Start            End              Type  Open Ref GrpRef Name
        0000022622dc8000 0000022622dcd000 exe   1    0   0      /usr/bin/perl
        000002285bdc7000 000002285c133000 rlib  0    1   0      /usr/lib/
        00000228c7de6000 00000228c7e16000 rlib  0    2   0      /usr/lib/
        000002282f00d000 000002282f101000 rlib  0    2   0      /usr/lib/
        0000022914fb2000 0000022914fb2000 0    1   0      /usr/libexec/

So I start with this initial guess to build the chroot. I run the following as root:

mkdir -p /var/www/usr/{bin,lib,libexec}
cp /usr/bin/perl /var/www/usr/bin/
cp -p /usr/lib/lib{c,m,perl}.so* /var/www/usr/lib/
cp /usr/libexec/ /var/www/usr/libexec/

We need to turn on slowcgi:

$ doas rcctl enable slowcgi
$ doas rcctl start slowcgi

Then we run:

$ doas chroot -u www -g daemon /var/www perl

I test some random gibberish to make sure perl works inside the chroot:

print "shibboleth";

Then ctrl+d to escape; and since it echoes shibboleth, it works.

Next, I create the directory to hold perl scripts:

mkdir -p /var/www/htdocs/perl/

Now I put an in /var/www/htdocs/perl/ just to see if the web server loads it:

#!/usr/bin/perl -w
use strict;
print "Content-Type:text/html\n\n";
print "This is the index file for\n";

Make sure to set the proper permissions:

$ doas chown -R www:daemon /var/www/htdocs/perl/
$ doas chmod +x /var/www/htdocs/perl/

At this point I try running this command:

$ curl

I get a 500 Internal Error, which means perl is not able to execute properly.

So I search for missing perl libraries:

$ doas find / -iname '*perl*'

The interesting one is the folder /usr/libdata/perl5 . We definitely need these libraries, so I update my script for creating the chroot:

mkdir -p /var/www/usr/{bin,lib,libexec,libdata}
cp /usr/bin/perl /var/www/usr/bin/
cp -p /usr/lib/lib{c,m,perl,pthread,util,z}.so* /var/www/usr/lib/
cp /usr/libexec/ /var/www/usr/libexec/
cp -R /usr/libdata/perl5 /var/www/usr/libdata/
mkdir -p /var/www/{tmp,dev}
chown www:daemon /var/www/tmp
touch /var/www/dev/null