>perl -wMstrict -le
"my @words;
 ;;
 my $fname = '../../../../moby/mwords/354984si.ngl';
 open my $fh, '<', $fname or die qq{opening '$fname': $!};
 while (<$fh>) {
   chomp;
   next if m{ [^[:alnum:]-] }xms;
   push @words, $_;
   }
 close $fh;
 ;;
 @words = reverse sort @words;
 my $ok_one_letter = qr{\A [ai] \z}xmsi;
 my $ok_two_letter = qr{\A (?: be | my | is | at | do) \z}xmsi;
 my $ignore   = qr{\A ism | ismy \z}xmsi;
 my $ok_other = qr{\A (?! $ignore) .{3,} \z}xmsi;
 @words =
   grep { $_ =~ $ok_one_letter ||
          $_ =~ $ok_two_letter ||
          $_ =~ $ok_other
          }
   @words
   ;
 my $words = join '|', @words;
    $words = qr{ $words }xms;
 ;;
 print '---------------';
 for my $string ('www.thisismydomain.com', @ARGV) {
   my @chunks = $string =~ m{ $words }xmsog;
   printf qq{'$string' ->};
   printf qq{ '$_'} for @chunks;
   printf qq{\n};
   }
"  www.knowthyself.net  kXnowthyXself.net
---------------
'www.thisismydomain.com' -> 'this' 'is' 'my' 'domain' 'com'
'www.knowthyself.net' -> 'know' 'thyself' 'net'
'kXnowthyXself.net' -> 'nowt' 'self' 'net'