cgi_to_mod_perl - First steps needed to use mod_perl as a CGI replacement

As the README and other mod_perl documents explain, mod_perl as a CGI replacement is only a small piece of what the package offers. However, it is the most popular use of mod_perl, this document is here so you can cut to the chase.

Read the INSTALL document, in most cases, nothing more is required than:

 perl Makefile.PL && make && make install

For using mod_perl as a CGI replacement, the recommended configuration is as follows:

 Alias /perl/  /real/path/to/perl-scripts/

 <Location /perl>
 SetHandler  perl-script
 PerlHandler Apache::Registry
 Options +ExecCGI
 </Location>

`Location' refers to the uri, not a directory, think of the above as

 <Location http://www.yourname.com/perl>

Any files under that location (which live on your filesystem under /real/path/to/perl-scripts/), will be handled by the Apache::Registry module, which emulates the CGI environment. The file must exist and be executable, in addition, 'Options ExecCGI' must be turned on.

If you wish to have mod_perl execute scripts in any location based on file extension, use a configuration like so:

 <Files ~ "\.pl$">
 SetHandler perl-script
 PerlHandler Apache::Registry
 Options ExecCGI
 </Files>

Note that `ScriptAlias' does _not_ work for mod_perl.

I/O

If you are using Perl 5.004 most CGI scripts can run under mod_perl untouched. If you're using 5.003, Perl's built-in CWread() and CWprint() functions do not work as they do under CGI. If you're using CGI.pm, use CW$query->print instead of plain 'ol CWprint().

HEADERS

By default, mod_perl does not send any headers by itself, however, you may wish to change this:

    PerlSendHeader On

Now the response line and common headers will be sent as they are by mod_cgi. And, just as with mod_cgi, PerlSendHeader will not send a terminating newline, your script must send that itself, e.g.:

 print "Content-type: text/html\n\n";

If you're using CGI.pm and 'print CW$q->header' you do _not_ need CWPerlSendHeader On.

NPH SCRIPTS

To run a CGI `nph' script under mod_perl, simply add to your code:

 local $| = 1;

If you normally set PerlSendHeader On, add this to your httpd.conf:

 <Files */nph-*>
 PerlSendHeader Off
 </Files>

PROGRAMMING PRACTICE

CGI lets you get away with sloppy programming, mod_perl does not. Why? CGI scripts have the lifetime of a single HTTP request as a separate process. When the request is over, the process goes away and everything is cleaned up for you, e.g. globals variables, open files, etc. Scripts running under mod_perl have a longer lifetime, over several request, different scripts may be in the same process. This means you must clean up after yourself. You've heard:

 always 'use strict' and C<-w>!!!

It's more important under mod_perl Perl than anywhere else, while it's not required, it strongly recommended, it will save you more time in the long run. And, of course, clean scripts will still run under CGI!

TRAPS

See mod_perl_traps.

Read the SUPPORT file.

Apache::PerlRun(3)