Recently had to change a number of lines from
$self->assert(qr/some_pattern/, $string, $message)
$self->assert($string =~ qr/some_pattern/m, $message)
Not sure why – the $string was a multi-line XML fragment, and the pattern was a phrase containing / and . chars. May need to do some more testing to isolate the reason. Works with the change. /m should not be necessary to match against a multiline string, but failed without this switch for my particular test cases.