use strict;
use warnings;

my $pid = open my $CMD, "| sar -c 1 2 \&>/dev/null" or die $!;

while (1) {
   open my $STAT,'<',"/proc/$pid/stat" or die $!;
   my $state = (split /\s+/, <$STAT>)[2];
   close $STAT;

   if ($state eq 'Z') {
      close $CMD or die $!;
      waitpid($pid,0);
      last;
   }

   sleep 1;
}