c:\@Work\Perl\monks>perl -wMstrict -le
"my $s = 'xx-xx';
 ;;
 my $lbw = qr/(?<=\w)(?=\W)|(?<=\W)(?=\w)/;
 printf qq{$-[0] } while $s =~ m{ $lbw }xmsg;
 print qq{\n};
 ;;
 my $wb = qr{ (?<!\w)(?!\W) | (?<!\W)(?!\w) }xms;
 printf qq{$-[0] } while $s =~ m{ $wb }xmsg;
 print qq{\n};
 ;;
 printf qq{$-[0] } while $s =~ m{ \b }xmsg;
"
2 3

0 2 3 5

0 2 3 5