In regular expressions the boundaries ``++^++`` and ``++\A++`` can only match at the beginning of the input (or, in case of ``++^++`` in combination with the ``++MULTILINE++`` flag, the beginning of the line) and ``++$++``, ``++\Z++`` and ``++\z++`` only at the end.


These patterns can be misused, by accidentally switching ``++^++`` and ``++$++`` for example, to create a pattern that can never match.

