pcre_compile() failed: unrecognized character after (?<

[Phillip Oldham]

server {
    server_name   ~^test\.(?<domain>.+)$;

    location / {
        root  /sites/$domain;
    }
}

# nginx -t
[emerg]: pcre_compile() failed: unrecognized character after (?< in "^test\.(?<domain>.+)$" at "domain>.+)$" in /etc/nginx/vhosts/testdomain:11
configuration file /etc/nginx/nginx.conf test failed
# nginx -V
nginx version: nginx/0.8.29
built by gcc 4.1.2 20080704 (Red Hat 4.1.2-44)
TLS SNI support disabled
configure arguments: --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx --conf-path=/etc/nginx/nginx.conf --error-log-path=/var/log/nginx/error.log --pid-path=/var/run/nginx.pid --with-rtsig_module --with-select_module --with-poll_module --with-http_ssl_module --with-http_stub_status_module --with-http_gzip_static_module --with-http_dav_module --with-http_flv_module --with-http_xslt_module --with-http_random_index_module --with-http_image_filter_module --http-log-path=/var/log/nginx/access.log --with-md5=/usr/lib --with-sha1=/usr/lib --with-http_perl_module

Can't tell what I'm doing wrong. Advice please?