perl -wle 'system("ps uch $$");push @x, $i while ($i++ < 1_000_000);print "Elements in \@x: " . @x;; system("ps uch $$");'
xxx      2365  0.0  0.0   3152  1248 pts/0    R+   18:45   0:00 perl
Elements in @x: 1000000
xxx      2365 20.0  0.5  22992 21056 pts/0    R+   18:45   0:00 perl