Meta character
	
Description
\ 	Marks the next character as either a special character or a literal. For example, n matches the character n, 
	whereas \n matches a newline character. The sequence \\ matches \ and \( matches (.
^ 	Matches the beginning of input.
$ 	Matches the end of input.
* 	Matches the preceding character zero or more times. For example, zo* matches either z or zoo.
+ 	Matches the preceding character one or more times. For example, zo+ matches zoo but not z.
? 	Matches the preceding character zero or one time. For example, a?ve? matches the ve in never.
. 	Matches any single character except a newline character.
\d 	Matches a digit character.
\s  Matches any white space including spaces, tabs, form-feed characters, and so on.

x|y 	Matches either x or y. For example, z|wood matches z or wood. (z|w)oo matches zoo or wood.
[xyz] 	A character set. Matches any one of the enclosed characters. For example, [abc] matches the a in plain.
[a-z] 	A range of characters. Matches any character in the specified range. For example, [a-z] matches any 
	lowercase alphabetic character     
(pattern)    Matches a pattern and remembers the match. 
             To match parentheses characters ( ), use \( or \)

{n} 	n is a non-negative integer. Matches exactly n times. For example, o{2} does not match the o in Bob, 
	but matches the first two os in foooood. 
{n,m}  The m and n variables are non-negative integers. Matches the preceding character at least n and at most m times. 
	For example, o{1,3} matches the	first three os in fooooood. The o{0,1} expression is equivalent to o?.
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EXEMPLOS: 
	CPF: por exemplo: 987654321-67  
	^\d{9}\-\d{2}$
	telefone fixo ou movel com ddd como em: (19)91234 5678 ou: (19)3521 5854 e tambem sem o espaco
	^\(\d\d\)\d{4,5}\s?\d{4}$
	EMAIL:
	^[a-z]+\.?[a-z]+@[a-z]+\.[a-z]+\[a-z]{2,3}$
Explicacao para o EMAIL:
	cadeia de letras minusculas com pelo menos 1 caracter seguida opcionalmente de um "." seguida de cadeia com uma ou mais letras minusculas
	seguida do caracter "@" seguida de cadeia com uma ou mais letras seguida de "." seguida de cadeia com uma ou mais letras mins. seguida de "."
	seguida de cadeia com 2 ou 3 letras minúsculas. 
	Casa com: celio.guimaraes@ic.unicamp.br mas não com celio@unicamp.br
EXERCICIO: 
	modifique (e simplifique) a expressao regular acima para casar com os 2 emails citados.
    Dica: use (pattern)  

Testador online neste site: https://www.regextester.com/