use My::Data;
my $schema = "My::Data";

my $acct = $schema->resultset( 'Accounts')->search({ acctid => 'pv001' })->single;

if($acct) {
     $acct->acctid( 'pv002' );
     $acct->update;
}
else {
     print "Could not find account to update!\n\n";
}