Regular expression quick start guide

Regular Expression Pattern	Explanations
^	Matches beginning of a line
$	Matches the end of a line
[characters]	Matches any single character between the brackets
re1|re2	Match either re1 or re2
re*	Matches zero or more occurrences of re
re+	Matches one or more occurrences of re
re?	Matches zero or one occurrences of re
Re{m,n}	Matches at least “m” and at most “n” occurrences of re
(...)	Parentheses are used to group regular expressions
\0, \1, \2, ...	Substitute the value matched by the nth grouped sub-expression, used in remapped fields.

Here are some examples:

Add 2720 prefix:

/(\d+)/2720\1/

or

/([0-9]*)/2720\1/

Strip first 4 digits:

/([0-9]{4})([0-9]*)/\2/