Thank you for taking time to reply. That might work in some environments, but it assumes that all of the servers use the same path prefix (/var/www). I don't believe that's true in our case. I suppose I could include a note in the installation instructions that the application name must be the final directory element in the AppBAse environment variable. Then I could use a regular expression something like this: 

m{^(/.+/MyApp/)$}

[download]

That should be sufficient to satisfy the untainting requirement, but I'm not sure whether it really makes the value "safe". Thanks again for responding so quickly.

In reply to Re^2: How to safely define a CGI program's application base directory by ddmiller
in thread How to safely define a CGI program's application base directory by ddmiller

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