SED is shorter (0 byte). SED /is/ a turing complete language [1] so don't try to claim that I'm cheating.
sed < input > output
[1] http://robertkotcher.com/sed.html
[update] s/set/sed/
sed < input > output
[1] http://robertkotcher.com/sed.html
[update] s/set/sed/
perl -pe '' <input >outputI was referring to an empty SED-program that would then be run via 'sed -f empty-file.sed'. Of course you need >0 bytes to invoke the SED program.