$string = "(x1,x1)(x2,y2)........(xn,yn)"

##</code><code>##

>perl -wMstrict -le
"my $u =
   '(x1,y9)(x11,y8)(x1,y7)(x11,y6)(x2,y5)(x22,y4)(x2,y3)(x22,y2)';
 ;;
 my $s =
   join  '',
   map   { $_->[0] }
   sort  { $a->[1][0] <=> $b->[1][0] || $a->[1][1] <=> $b->[1][1] }
   map   { [ $_, [ $_ =~ m{\d+}xmsg ]] }
   split m{ (?<= \)) (?= \() }xms,
   $u
   ;
 ;;
 print qq{'$s'};
"
'(x1,y7)(x1,y9)(x2,y3)(x2,y5)(x11,y6)(x11,y8)(x22,y2)(x22,y4)'

##</code><code>##

>perl -wMstrict -le
"my $u =
   '(x1,y9)(x11,y8)(x1,y7)(x11,y6)(x2,y5)(x22,y4)(x2,y3)(x22,y2)';
 ;;
 use constant WIDTH => 10;
 my $s =
   join  '',
   map   { substr $_, WIDTH+WIDTH }
   sort
   map   { sprintf '%0*4$d%0*4$d%s', m{\d+}xmsg, $_, WIDTH }
   split m{ (?<= \)) (?= \() }xms,
   $u
   ;
 ;;
 print qq{'$s'};
"
'(x1,y7)(x1,y9)(x2,y3)(x2,y5)(x11,y6)(x11,y8)(x22,y2)(x22,y4)'