>perl -wMstrict -le
"my $s = 'xxxx yy zzzzz xxxx qqq xxxx yy zzzzz xxxx qqq';
 ;;
 for my $ar ([2, 4, 3], [5, 3]) {
   my $rx = rxg(@$ar);
   print $rx;
   my @groups = $s =~ m{ $rx }xmsg;
   print qq{'$_'} for @groups;
   }
 ;;
 sub rxg {
   my ($rx) =
   map qr{ \b $_ \b }xms,
   join ' \b .+? \b ',
   map qq{\\w{$_}},
   @_
   ;
   ;;
   return $rx;
   }
"
(?^msx: \b \w{2} \b .+? \b \w{4} \b .+? \b \w{3} \b )
'yy zzzzz xxxx qqq'
'yy zzzzz xxxx qqq'
(?^msx: \b \w{5} \b .+? \b \w{3} \b )
'zzzzz xxxx qqq'
'zzzzz xxxx qqq'