open(my $fh, '<:encoding(UTF-8)', $qfn)
    or die("Can't open file \"$qfn\": $!\n");

##</code><code>##

s/([0-9]{3})-([0-9]{3})/$1\x{2014}$2/g

##</code><code>##

s/(?<=[0-9]{3})-(?=[0-9]{3})/\x{2014}/g