I have come across a philosofical issue. Is there a good method for detecting if a module has been loaded from within a subroutine?

In more detail: I am planning in writting a common authentication subroutine what will be used across several utilities being implemented on my intranet. Most of these utilities will need to validate a user against a MySQL table, and return true or false. Now, since some of these scripts are already written, and some of then don't use DBI, I was planning on writting something in the lines of: 
sub AuthenticateUser {
  my ($username,$password,$service) = @_;

  # this is my question
  if (DBI is not loaded and connected) {
    eval {  use DBI;  };
    if ($@) { die($@); }
  }
  # go on and do stuff with $dbh
  # select warp.username,warp.password,services.service
  # from warp,services where blah blah blah
  return($service);
}

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I haven't even looked at perldoc, since I don't know where to start! Any suggestions, pointers?

In reply to Detecting modules in use? by BBQ

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