the brackets match character classes i.e. a one of match you want something like 

!/mystring/

[download]

This will reject any input string with the text 'mystring' in it.

Yours would find any text which had no (,),m,y,s,t,r,i,n,g characters in it at all.

In reply to Re: "everything but" regex by dga
in thread "everything but" regex by melguin

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