I use placeholders for all my queries (mainly for security). The
problem I have is that I need to be able to print the actual queries
my code runs into a log.... with the placeholders replaced.

For example, consider the following:

my $id = "example";
my $sql = "UPDATE Customers SET ID=?";
my $query = $db->prepare($sql);
$query->execute($id);

How do I print the ACTUAL query that was run into a log file.... with
the placeholders replaced???

For example, when I do the following:

print $sql;

It prints:

UPDATE Customers SET ID=?

When I need it to print:

UPDATE Customers SET ID='example'

I know that I could replace the placeholders myself... but then
again... I need to log the ACTUAL query that was just executed... or
attempted to be executed.

    my $log_sql = $sql;
    $log_sql =~ s{\?}{'$_'} for @values;
    print $log_sql;

the array @values keeps all the binding values to the placeholders,
for your case, it's

    my @values = qw($id);

you can pack this into a subroutine, i.e.

sub printSQL {
    my $sql = shift;
    print $sql and return if not @_;
    $sql =~ s{\?}{'$_'} for @_;
    print index($sql, '?') > 0 ? "need more binding values\n" : $sql;