Your regular expression seems to work fine.. it's kind of hard to read, but I assume the regular expression is supposed to be

/[^a-zA-Z0-9_]/
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First off, you don't need to negate the return value of the regular expression.. it's fine as it is. The only suggestion I could give would be that you might instead want to simplify by saying:

/[^\w]/
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As the \w metacharacter is equal to exactly a-zA-Z0-9_. To simplify further:

/\W/
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As \W is the opposite of \w