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Check if a user name contains non-alphanumeric characters


On my web site, a user may put in a desired user name and I have to check that it only contains letters, digits, or the @ and . characters. How can I do that with a regular expression (regex)?


The allowed characters are described as A-Za-z0-9.
That are the intervals A-Z, a-z and 0-9. You can also substitute 0-9 with d (digit).

To check for the undesired character, use the ^ operator in front of it as shown below:

if ($username =~ /([^A-Za-z0-9@.])/) {
   print "Problem in user name with '$1'";

Generated 20:01:39 on Oct 27, 2020