How to use postgres dbd placeholders for DB Object names - perl

Question

(or How to iterate thru information schema Using perl DBI (DBD::PG) and placeholders?)
Windows 7, ActiveState Perl 5.20.2, PostgreSQL 9.4.1 .
Cases A, B and C below were successful when using a placeholder for a COLUMN VALUE. In order
no placeholder used
passed a literal
passed a variable (populated with same literal)
It would be great to raise it up a level to DB Objects.. (tables, views etc)
Here's the output with the error for Case D:
Z:\CTAM\data_threat_mapping\DB Stats\perl scripts>test_placeholder.pl
A Row Count: 1
B Row Count: 1
C Row Count: 1
DBD::Pg::st execute failed: ERROR: syntax error at or near "$1"
LINE 1: SELECT COUNT(*) FROM $1 WHERE status = 'Draft';
^ at Z:\CTAM\data_threat_mapping\DB Stats\perl
scripts\test_placeholder.pl line 34.
Much obliged for any direction!
#!/usr/bin/perl -w
use strict;
use diagnostics;
use DBI;
my $num_rows = 0;
# connect
my $dbh = DBI->connect("DBI:Pg:dbname=CTAM;host=localhost",
"postgres", "xxxxx",
{ 'RaiseError' => 1, pg_server_prepare => 1 });
#---------------------
# A - success
my $sthA = $dbh->prepare(
"SELECT COUNT(*) FROM cwe_compound_element WHERE status = 'Draft';"
);
$sthA->execute(); # no placeholders
#---------------------
# B - success
my $sthB = $dbh->prepare (
"SELECT COUNT(*) FROM cwe_compound_element WHERE status = ?;"
);
$sthB->execute('Draft'); # pass 'Draft' to placeholder
#---------------------
# C - success
my $status_value = 'Draft';
my $sthC = $dbh->prepare(
"SELECT COUNT(*) FROM cwe_compound_element WHERE status = ?;"
);
$sthC->execute($status_value); # pass variable (column value) to placeholder
#---------------------
# D - failure
my $sthD = $dbh->prepare(
"SELECT COUNT(*) FROM ? WHERE status = 'Draft';"
);
$sthD->execute('cwe_compound_element'); # pass tablename to placeholder
I've tried single/double/sans quotes (q, qq)...

Answer 1

If
SELECT * FROM Foo WHERE field = ?
means
SELECT * FROM Foo WHERE field = 'val'
then
SELECT * FROM ?
means
SELECT * FROM 'Table'
and that's obviously wrong. Placeholders can only be used in an expression. Fix:
my $sthD = $dbh->prepare("
SELECT COUNT(*)
FROM ".$dbh->quote_identifier($table)."
WHERE status = 'Draft'
");
$sthD->execute();