How do I reverse regex substitution?

How do I reverse regex substitution?

References

Reference NO 1

http://stackoverflow.com/questions/15188534/how-do-i-reverse-regex-substitution

Reference NO 2

http://stackoverflow.com/questions/8264391/notepad-inverse-regex-replace-all-but-string

Reference NO 3

http://msdn.microsoft.com/en-us/library/vstudio/e47f3dkc(v=vs.100).aspx

Reference NO 4

http://www.cs.utah.edu/dept/old/texinfo/emacs18/emacs_17.html

Reference NO 5

http://langref.org/all-languages/pattern-matching/replacing/replace-all-regex-matches-in-a-string-with-a-dynamic-string

Reference NO 6

http://www.codingforums.com/archive/index.php/t-7742.html

Reference NO 7

http://www.template-toolkit.org/docs/manual/VMethods.html

Reference NO 8

http://ruby-doc.org/core/String.html