ALPHANUM
A..Z, a..z, 0..9	match themself

DOT
.	match any char

REPEAT	must appear after some element to be repeated
?	0 or 1 char ( equal to {0, 1} )
+	1 or more chars ( equal to {1, } )
*	0 or more chars ( equal to {0, } )
{n,}	n or more chars
{,m}	0 or more chars, up to m
{n,m}	n or more chars, up to m
{n}	exactly n chars

ASSERTIONS
^	Matches the starting position within the string.
$	Matches the ending position of the string or the position just before a end of line

SUB-EXPRESSIONS
(exp)	exp is subexpression

Examples

Text	RegEx	Result
gfksafdh W0123456 sdsfsdfsaf	W[0-9]+	W0123456
gfksafdh W0123456 sdsfsdfsaf	W[012345]+	W012345
gfksafdh W0123456 sdsfsdfsaf	.[0,1,2,3,4,5,6]+	W0123456
gfksafdh W0123456 sdsfsdfsaf	[A-Z,0-9]*	W0123456
MeaJNN: 71C61 ZooTemt	[0-9][A-z]*	71C61
Comentar #1 / 20.02.2021 - 16:00 / from: John Doe	[0-9,\:]{5}	16:00
Email from AJ to service@stepover.de was send yesterday	[A-z,0-9]+@[A-z, 0-9]+\.[A-z]+	service@stepover.de
1 2 21.2.2021 33 44.A	[0-9]{1,2}\.[0-9]{1,2}\.[0-9]{2,4}.	21.2.2021
2021-01-12 13:52:56 W090001, 01.01...V9... 10x10_FHA100_DT 3,0_Bol 0,5 / MU Per Fraction 52.5 Beam I-000 re Beam I-000 re	[0-9]+\.[0-9] (Leerzeichen am Ende!)	52.5
urn:cid:199606121851.1@bar.example.com	@[^\.]+\.	@bar.

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