Others

Anchors

^The match must start at the beginning of the string or line.
$The match must occur at the end of the string or before \n at the end of the line or string.


Backreference Constructs

\numberBackreference. Matches the value of a numbered subexpression.
\k<name>Named backreference. Matches the value of a named expression.


Alternation Constructs

|Matches any one element separated by the vertical bar (|) character.
(?(expression)yes|no)Matches yes if expression matches; otherwise, matches the optional no part. expression is interpreted as a zero-width assertion.
(?(name)yes|no)Matches yes if the named capture name has a match; otherwise, matches the optional no.