I found the problem. It had to do with the fact that your version doesn't respect $_, while mine does.

sub r2{
$_=$_[0];y/2569347/5296/;pop==reverse
}

my @tests = (0..9);
print "$_: ",(r2($_)?'Yes':'No'), "\n" for @tests;

__DATA__
0: Yes
1: Yes
2: Yes
3: Yes
4: Yes
5: Yes
6: Yes
7: Yes
8: Yes
9: Yes
[download]

Because of the way I was calling your function, I saw something wrong. However, I mistook what I saw wrong and I apologize for not knowing tr/// as well as I should have.