use strict;
use warnings;


problem([1,2,3]);

sub problem {
    print2DArray(@_);  #Output: 1 2 3
    reverseArray1(@_);
    print2DArray(@_);  #Output: 1 2 3
    reverseArray2(@_);
    print2DArray(@_);  #Output: 3 2 1
}

sub reverseArray1 {
    my @arr = @_;
    for my $i (0 .. $#arr) {
        $arr[$i] = [reverse @{$arr[$i]}];
    }
}

sub reverseArray2 {
    my @arr = @_;
    for my $i (0 .. $#arr) {
        @{$arr[$i]} = reverse @{$arr[$i]};
    }
}

sub print2DArray {
    for my $i (0 .. $#_) {  # How does that work for the nested for lo
+op?
        for(my $j=0;$j<scalar(@{$_[$i]});$j++){  # $#_[$i] doesn't wor
+k
            print $_[$i][$j]," ";
        }
        print "\n";
    }
}
[download]

$arr[$i] = [reverse @{$arr[$i]}];
[download]

@{$arr[$i]} = reverse @{$arr[$i]};
[download]