Since you were talking about config parameters and such....

I usually have a package that defines some constants, and use it like

  use My::Constants qw/ MY_FOO MY_BAR MY_LOGFILE_NAME /;

  my $fh = IO::File->new( MY_LOGFILE_NAME );
  ....
[download]

My::Constants has default values for those constants, and optionally overrides those values with values that it reads from a XML config file , or from %ENV

I do this instead of using a config hash or something mainly because I wanted a compile time check of config variable names