$regexp(%TITLE%,[^0-9a-zA-Z],) does not work

Mac
6

The documentation on Scripting Functions states for $regexp:

Please note that you have to escape comma and other special characters in expr.

So the most easiest way would be to just enclose the expression in ' (given that [ and ] are special characters in Mp3tag's Format Strings and Available Placeholders)

$regexp(%TITLE%,'[^0-9a-zA-Z]',)