Usually my code starts out as

my $results = $dbh->selectall_arrayref(<<'SQL',{ Slice => {} }, $place
+holder1, ... );
    SELECT foo
         , bar
      FROM mytable
SQL
[download]

Then, while debugging, it morphs into

my $sql = <<'SQL';
    SELECT foo
         , bar
      FROM mytable
SQL
$app->log($sql);
my $results = $dbh->selectall_arrayref($sql,{ Slice => {} }, $placehol
+der1, ... );
[download]

... and then it stays that way, because reverting the structure is only good until I need to re-debug things:

my $sql = <<'SQL';
    SELECT foo
         , bar
      FROM mytable
SQL
# $app->log($sql);
my $results = $dbh->selectall_arrayref($sql,{ Slice => {} }, $placehol
+der1, ... );
[download]

For the placeholders I agree. Sometimes I keep the placeholders in an array to mention them in the same place as the SQL. In other situations, I use named placeholders like SQLite supports nowadays, and bind those in a loop:

    while (my ($name,$value) = each %$parameter_names) {
        (my $perl_name) = ($name =~ m!(\w+)!);
        $perl_name = '$' . $perl_name;
        if( ! exists $parameters->{$perl_name}) {
            croak "Missing bind parameter '$perl_name'";
        };
        my $type = SQL_VARCHAR;

        # This is a horrible API, but so is using uplevel'ed variables
        if( my $r = ref $parameters->{$perl_name}) {
            if( $r eq 'SCALAR' ) {
                $type = SQL_INTEGER;
                # Clear out old variable binding:
                my $v = $parameters->{$perl_name};
                delete $parameters->{$perl_name};
                $parameters->{$perl_name} = $$v;
            } elsif( $r eq 'ARRAY' ) {
                $type = SQL_INTEGER;
                # Clear out old variable binding:
                my $v = $parameters->{$perl_name};
                delete $parameters->{$perl_name};
                $parameters->{$perl_name} = $v->[0];
                $type = $v->[1];
            }
        }
        $sth->bind_param($name => $parameters->{$perl_name}, $type)
    };
[download]

See Filesys::DB for a fancy but ultimately pointless idea of binding placeholder names to lexical variables in the Perl code. This was nice to use but in the end, the surrounding program does not pass SQL around but has function/method calls that do the right thing and the lexical binding does not provide anything helpful at the outside surface.

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