Perl DBI->Connect: how to detect a a lost connection

Hi: I have a script which connects to a database when it starts up
$dbh = DBI->connect("dbi:Pg:dbname=$dbname;host=$host;port=$port;","$username", "$password", {AutoCommit => 1});
followed by a while loop which runs a query for this connection at 60 second intervals. If the database goes down for some reason, I want the script to try reconnecting to the database. How do I figure out within the while look if the database connection is still valid. If tried using the $dbh variable (if ($dbh)then connection is fin. else connection is bad). That doesn't seem to work. How do I figure out if the $dbh connection has been lost within the while loop?
Any suggestions.
TIA
Ravi



.