An alternative approach is to match the lines you want to see:

use strict;
use warnings;
while(<DATA>){
        print if /^\s+\d\s+\d\s+/;
}
__DATA__
procs -----------memory---------- ---swap-- -----io---- --system-- ---
+--cpu-----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us s
+y id wa st
 0  0      0 50101200 234628 9636240    0    0     0    34 10782 6802 
+ 1  1 98  0  0
 1  0      0 50102044 234628 9636276    0    0     0    96 8630 6980  
+1  1 98  0  0
 1  0      0 50113020 234628 9626112    0    0     0  3092 13393 10324
+  3  1 96  0  0
 1  0      0 50111244 234628 9628188    0    0     0  1540 10106 8874 
+ 2  1 97  0  0
 0  0      0 50111256 234628 9628228    0    0     0     0 8674 6961  
+1  1 98  0  0
 0  0      0 50109884 234628 9628228    0    0     0   280 11290 7593 
+ 1  1 97  0  0
 0  0      0 50110672 234628 9628264    0    0     0    16 8886 7301  
+1  1 98  0  0
 1  0      0 50110708 234628 9628268    0    0     0    40 11285 6833 
+ 1  1 98  0  0
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