package TArtLib;
use strict;
use vars qw($dbh);
...
sub dbh {
  return $dbh;
}

##</code><code>##

package TArt::Editor;
use TArtLib;
...
my $dbh = TArtLib->dbh;

##</code><code>##

sub dbh {
  unless ($dbh) {
    # connect to the database now.
  }
  return $dbh;
}