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

Try

foreach my $a (@_ = @ar)

now modifying $a does not modify @ar. Works for me on v5.20.2