A1=0 1 2 3 4 5 6 7 
A2=6 7

##</code><code>##

foreach my $A1 (@cpu_lists)
@A2 = @{$A1}[-n..-1]; #A2 is derived from A1
@{$A1} = splice @{$A1},6,-1;#A1 should be spliced to remove elements of A2

where n = number of elements which we want in A2.