perl wants "use utf8" when UTF-8 is in the source

When there are literal UTF-8 characters in the source, "use utf8" will
tell Perl to set the utf8 flag on strings.
require at least Perl 5.6

The core modules and pragmas being used require at least Perl 5.6 in
order to work. Explicitly saying "use 5.006" will make the error more
clear.
do not buffer STDOUT

This ensures that the status line printed to STDERR at the very end of
the script will appear after all other script output.
also ignore vim swapfiles
Merge pull request #27 from preaction/perl-changes

Perl changes