A NEWLINE character in string will not be matched by a period outside bracket expression or by any form of a non matching list.

A circumflex (^) in pattern when used to specify expression anchoring will match the zero length string immediately after a newline in string, regardless of the setting of REG_NOT_BEGINOFLINE.

A dollar-sign ($) in pattern when used to specify expression anchoring, will match zero-length string immediately before a new line in string, regardless of the setting of REG_NOT_ENDOFLINE.

If not specified (strict), the search is sucessful if the WLD is within a calculated limit where each insertion, deletion and replacement adds a weight to a common pool of weights. This is the mathematically correct WLD.

From a user's point of view the strict WLD is an exclusive-OR of the arguments given, for example if allowed insertions=2 and allowed replacements=2, the search fails if 2 characters had been inserted and an additional operation would be needed to match. Depending on the weights it may also fail if 1 character was inserted and 1 character replaced and an additional operation would be needed to match. The strict algorithm may match less than expected from a first glance of the specified arguments, but does not return false positives.

If specified (relaxed), the search is also successful if the combined pool for insertions and deletions is below a doubled calculated limit and replacements are treated differently. Additionally, swapped characters are counted as one replacement.

From a user's point of view the relaxed WLD is an inclusive-OR of the arguments given, for example if allowed insertions=2 and allowed replacements=2, the search succeeds if 2 characters had been inserted and an additional replacement is needed to match. The relaxed algorithm may return false positives, but meets user expectation better.