tr/\xe9/FIX/d is the same as tr/\xE9/F/ and convert chr(0xE9) to "F".

tr/\00233/FIX/d is the same as tr/3\002/IF/ and converts chr(002) to "F" and "3" to "I".

What am I doing wrong?

What are you trying to do?

You previously alluded that you wanted to remove "é" characters that were encoded as E9.

perl -i -pe 'tr/\xE9//d' yourprogram.pl
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But the "FIX" in the new code seems to indicate you want something else.