If you want to keep @bigList unchanged then you could use another array to keep start and end positions for each list added, something like this

#!perl;
use strict;
use warnings;

my @test = ([ qw(A B C) ],[ qw(1 2 3 4)], [qw( x y )]);
my @bigList = ();
my @chunk = ();
for my $ar (@test){
  my @templist = @$ar;
  my $start = scalar @bigList;
  push @bigList,@templist;
  my $end = $#bigList;
  push @chunk,[$start,$end];
}
print "@bigList \n";

# each smaller list
for my $ar (@chunk){
  my ($start,$end) = @$ar;
  print "@bigList[$start..$end] \n";
}
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