Your PerlSetVar idea is good. You can set a key there that you use to pull the values from a hash in your startup.pl or a similar config file. You can also do something where you pass a value to the httpd and use that to switch between sets of PerlSetVars in httpd.conf.

On command-line:

> httpd -DPROD
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In httpd.conf:

<IfDefine PROD>
  PerlSetVar DATABASE_NAME foo
  PerlSetVar DATABASE_USER bar
  PerlSetVar DATABASE_PASS baz
</IfDefine>
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You can do fancier stuff too. In one place that I worked, we used a small script with Template Toolkit to re-generate httpd.conf for different environments based on a small file of values keyed on different environments. It was nice because we had the ability to do inheritance, where we would define defaults and override them for development or other special cases.