perl -i -pe '(code that runs but does the wrong thing)'  `find . -name '*.TXT'`

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perl -i.bak -M'open IO => ":encoding(UTF-16LE)"' -pe 'BEGIN{undef $/} s/(?<=\x{feff})/Filename: $ARGV\n/'  `find . -name '*.TXT'`

##</code><code>##

find . -name '*.TXT' | xargs perl -i.bak ...