>perl -wMstrict -le
"$a = join ' ', 0 .. 7;
 sub fold (&) {
   local $_;
   my @a;
   push @a, $_ while $_[0]->();
   return @a;
   }
 use Data::Dumper;
 print Dumper fold {
   return $_ = $a =~ /(\w) (\w)/g ? [ $1, $2 ] : undef;
   };
"
$VAR1 = [
          '0',
          '1'
        ];
$VAR2 = [
          '2',
          '3'
        ];
$VAR3 = [
          '4',
          '5'
        ];
$VAR4 = [
          '6',
          '7'
        ];