Do you mean the grep program or Perl's grep? Whatever, the answer is no. As I feel kind, the correct solution is (or {s,c}ould be)

s/[\[\]]//g;
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Since this is only a hint I'll also tell you about

perl -lpi -e '...'
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separately. It is left as an exercise to the reader to check up the documents or any introductory Perl book and put it all together.