Are you familiar with perl's -n and -p switches?

http://perldoc.perl.org/perlrun.html#*-n*

Those "flt" lines could be written

  perl -lpe 's|\s+| |gsi' file.txt
  find . | perl -ne 'if (-f) { print -s }'

(-l chomps the incoming newlines, and puts them back on the output)

Of course, "perl -ne" is longer than "flt", and I appreciate all this implicit use of $_ is not to everyone's tastes.