How to escape asterisk in regexp?

How to escape asterisk in regexp?

References

Reference NO 1

http://www.regular-expressions.info/characters.html

Reference NO 2

http://stackoverflow.com/questions/2801549/how-do-i-replace-an-actual-asterisk-character-in-a-regex-expression

Reference NO 3

http://msdn.microsoft.com/en-us/library/4edbef7e.aspx

Reference NO 4

http://www.coderanch.com/t/408248/java/java/Match-asterisk-regexp

Reference NO 5

http://www.perlcode.org/tutorials/procmail/regular_expressions.pod

Reference NO 6

http://www.voip-info.org/wiki/view/Asterisk+func+regex

Reference NO 7

http://objectmix.com/pegasus/203110-how-match-literal-asterisk-regular-expression-filter.html

Reference NO 8

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