If the connection is refused, then the prepare should cause an error that exits the script (right?).

Only if you told it to! There are 2.5 ways of doing this. First way (least pretty):

$sth = $dbh->prepare( "select blah from table" )
    or die "Prepare failed: ", $dbh->errstr;
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Second way:

$dbh->{RaiseError} = 1;
$sth = $dbh->prepare( "select blah from table" )
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Both previous ways work, but kill your script and don't offer a clean way to close the transaction (if you are using transactions). Try this, way 2.5:

$dbh->{RaiseError} = 1;
eval {
  my $sth = $dbh->prepare("select blah from table");
  $sth->execute();
};
if ($@) {
  warn "Transaction aborted: $@";
  eval { $dbh->rollback };
  die "Unable to rollback: $@" if $@;
}
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