Dynamic code is also very hard to debug. I would recommend something like the following, to help you find out when/where it has errors.

$code = "print 'Hello World.'";
$sub = eval "sub { $code }";
unless ($sub) {
  # ack! it failed to eval
  # lets leave a note about the code, and the error
  # so we can debug this.
  die sprintf('CODE: %s\n\nERROR: %s\n\n', $code, $@);
}
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