perl -e 'while (<>) { print "XXX\n" ;print; print "XXX" }'

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perl -ne 'print "XXX\n" ;print; print "XXX"'

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perl -pe '$_ = "XXX\n" . $_ . "XXX"'

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perl -e'...' < /tmp/file

##</code><code>##

perl -e'...' /tmp/file

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perl -pe '$_ = "XXX\n" . $_ . "XXX"' /tmp/file