Why is Perl foreach variable assignment modifying the values in the array?

Question

OK, I have the following code:

use strict;
my @ar = (1, 2, 3);
foreach my $a (@ar)
{
  $a = $a + 1;
}

print join \", \", @ar;

and the outp

Answer 1

$a in this case is an alias to the array element. Just don't have $a = in your code and you won't modify the array. :-)

If I remember correctly, map, grep, etc. all have the same aliasing behaviour.