It behaves exactly as you want it to, for me. But I'm using Oracle, not postgres, and I get back:

DBD::Oracle::db prepare failed: ORA-00936: missing expression (DBD ERR
+OR: OCIStmtExecute/Describe) at t.pl line 17, <A> line 2.
DBD::Oracle::db prepare failed: ORA-00936: missing expression (DBD ERR
+OR: OCIStmtExecute/Describe) at t.pl line 17, <A> line 2.
[download]

Note that it's an Oracle error. Maybe postgres just doesn't complain about such things?

Unfortunately, my link to my home machine has just gone down, so I can't compare at the moment

BTW, although you open testexec.out, you don't print to it. But that's irrelevant, given the earlier problem