Perl script Mysql update help

[Neil Bernard]

Ok I give up, i've read loads of posts I just cannot get this snippet work with variables, works fine if I use manual values.... Please help

$sql = 'UPDATE snmpcol SET sysUpTime = "$snmpresult" WHERE IP = "192.168.1.60"';
$sth = $dbh->prepare($sql) or die "Cannot prepare: " . $dbh->errstr();
$sth->execute() or die "Cannot execute: " . $sth->errstr();
$sth->finish();

Thanks in advance chaps