#### or with placeholders:
my(@col_names, $sth);
{
    local $" = ',';
    @col_names   = keys %data;
    my $val_spec = join ',', ('?') x @col_names;
    my $sql      = "insert into my_table (@col_names) values ($val_spec)";
    $sth = $dbh->prepare($sql);
}