If your CGIs run as the user who created them instead of the webserver (ie, setuid through something like Apache's suEXEC), then you can fallback to getpwuid if $ENV{'HOME'} is unset.

my $HOME = $ENV{'HOME'} || ( getpwuid $> )[7] 
  or die "Uh oh, I've been evicted...\n";
[download]

If you're feeling particularly dangerous, you could also try falling back to the current directory (|| ".") if neither $ENV{'HOME'} or getpwuid return something useful, with the caveat being the current directory may not always be what you expect it to be.

However, I find such a solution limiting: what if you want to run the same app with different configurations? Not possible unless you subvert $ENV{'HOME'}.

A better way might be to have each of your apps explicity set where their config directory (or better yet, the config file itself) should be, and then optionally have ProgConfig.pm fallback to the $ENV{'HOME'}-style above if they didn't.

Something like...

package ProgConfig;

sub import {
  my $package    = shift;

  my $config_dir = shift || $ENV{'HOME'} || ( getpwuid $> )[7] 
    or die "Shazbot! Where's my config dir at?\n";

  # do whatever to load config
}
1;
[download]

Which you'd then call from your apps as...

use ProgConfig '/path/to/my/config_dir';

    --k.