{
   package Cow;
   my $i;
   sub moo { print(("moo " x ++$i), "\n"); }
}

Cow->moo();  # moo 
Cow->moo();  # moo moo 
Cow->moo();  # moo moo moo 

##</code><code>##

{
   package MyDB;
   my $DBH;
   sub dbh {
      if ($DBH) {
         print "found existing $DBH\n";
      } else {
         $DBH = 'dbh';
         print "Init $DBH\n";
      }
   }
}

MyDB->dbh();  # Init dbh
MyDB->dbh();  # Found existing dbh
MyDB->dbh();  # Found existing dbh