Regular Expressions 101

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[0-9a-z !]*
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Match a single character present in the list below
[0-9a-z !]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case insensitive)
a-z matches a single character in the range between a (index 97) and z (index 122) (case insensitive)
!
matches a single character in the list ! (case insensitive)
Global pattern flags
i modifier: insensitive. Case insensitive match (ignores case of [a-zA-Z])
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
g modifier: global. All matches (don't return after first match)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

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Test String