In addition to this, for the case when the key starts with "-" ( if (/^-/) ),
You are not appending to $names.

The "for" loop and "chop"s could be replaced by:

my $names = join ",\n", map {s/^-//; $_ } keys %data;
my $values= join ",\n", map { m/$-/ ? $data{$_} : $dbh->quote($data{$_
+} } keys %data;
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(I have made some assumptions on what you want done when the key starts with "-".)