you can use Config::Find to find the configuration file, it will look in all the common places for it, for instance...

use Config::Find;
my $cfg_fn = Config::Find->new(name=>'foo');
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will look for it on

  ~/.foo
  ~/.foo.conf
  ~/.foo.cfg
  $FOO_HOME/etc/foo.conf
  $FOO_HOME/etc/foo.cfg
  /etc/foo.conf
  /etc/foo.cfg
[download]