c:\@Work\Perl>perl -wMstrict -le
"use Data::Dump qw(pp);
 ;;
 my $qr_string = q((?:(\w)\W{2}(\w))*);
 my $qr = qr[$qr_string];
 ;;
 my $s = '%%%%';
 ;;
 print 'match @ offset ', $-[0], '  ($1, $2)==', pp $1, $2  while $s =~ /$qr/g;
 ;;
 my @captures = $s =~ /$qr/g;
 pp \@captures;
"
match @ offset 0  ($1, $2)==(undef, undef)
match @ offset 1  ($1, $2)==(undef, undef)
match @ offset 2  ($1, $2)==(undef, undef)
match @ offset 3  ($1, $2)==(undef, undef)
match @ offset 4  ($1, $2)==(undef, undef)
[undef, undef, undef, undef, undef, undef, undef, undef, undef, undef]