use strict;
use warnings;

use feature qw( say );

use Inline C => <<'__EOS__';

   void testing(char* s) {
      s[0] = 'y';
   }

__EOS__

my $x = "x";
my $y = $x;
say "$x-$y";
testing($y);
say "$x-$y";

##</code><code>##

x-x
y-y   <-- Changed both $x and $y

##</code><code>##

for (1..2) {
   my $y = "x";
   say $y;
   testing($y);
}

##</code><code>##

x
y     <-- Changed the constant!