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return doesn't change @_.

@_ is an array of aliases to the actual arguments, so changing @_ changes the actual arguments.

sub { ++$_ for @_ }->(my @arr = 'a' .. 'c'); print "@arr"; # Output: b c d

In your case, it's bit more complex. Changing the function to

sub reverseArray { my @arr = @_; for my $i (0 .. $#arr) { @{ $arr[$i] } = reverse @{ $arr[$i] }; } }
wouldn't have helped, as you're working with an array of arrays. The inner arrays are represented as references, so even if you store the references in a different @arr, they still refer to the same inner arrays.

To keep the array unchanged, only assign to the copy, don't change the references from the original array.

sub reverseArray { my @arr = @_; for my $i (0 .. $#arr) { $arr[$i] = [ reverse @{ $arr[$i] } ]; } }
map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

In reply to Re: Array value changing for some reason by choroba
in thread Array value changing for some reason by Silt

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