# Example of using variable names for variables,
# that I find useful.

#-------------
# user defined code
# ------------
my $some_var_list = var_from_env_var("list");
my $some_var_source = var_from_env_var("source");
my $some_var_other  = var_from_env_var("other");
print "list=>  $some_var_list\n".
      "source=>$some_var_source\n".
      "other=> $some_var_other\n";

# ------------
# my module
# ------------
sub var_from_env_var {
    # could use this, or some other complex method
    # of determining the default value.
    my $list_def =   $ENV{"LIST_VAR"} 
                  || $ENV{"LIST_VAR_DEPRECIATED"} 
                  || "other_list";
    my $source_def = $ENV{"SOURCE_VAR"} 
                  || $ENV{"SECONDARY_SOURCE"} 
                  || "other_source";

    # is there another way to use a variable to point 
    # to a variable other than eval?
    my $input = shift;
    my $result = eval "\$$input"."_def";
    return $result if (defined ($result));
    return $input;
}