find patterns in text

Characterclassese: languagef of character wildcards

. any character except \n
\d any decimal digit
\D anything BUT a decimal digit.
\s whitespace ( space, \t, \n)
\S anything but whitespace
\w alphanumeric or underscore
\W all chars except \w s.
\b
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character class: wildcard for one character
[abc] -  matches a, b, or c
[a-z] -  - indicates a range 
[^0-9] - anything but a digit 


Multiplicity Operators