Thanks, I got it to print out using -p, but the substitution is not being printed in the output (parsed) file.

I know that the regex is working because when i run the following it prints the substituted words.

perl -F\t -lape "$F[4] =~ s/.*y.*/yes/; print $F[4], \"\n\";" results.
+txt
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Not sure why the substituted words aren't being written into the file. Any thoughts? Thanks!