I noticed that you tried to use the eval BLOCk form, not the the eval STRING form.

Those two uses of eval are two quite different beasts, and I guess that $^S refers to the string form, not to the block form.

Update Ok I tried it, I was wrong. Here's what's happening:

use strict;
use warnings;

use Data::Dumper;

print "in main: ",  Dumper $^S;

eval 'BEGIN { print "In eval STRING BEGIN: ", Dumper $^S; } print "in 
+eval STRING: ", Dumper $^S';
eval { 
    BEGIN { print "in eval BLOCK BEGIN: ",  Dumper $^S;} 
    print "in eval BLOCK: ", Dumper $^S;
};
__END__
in eval BLOCK BEGIN: $VAR1 = undef;
in main: $VAR1 = '0';
In eval STRING BEGIN: $VAR1 = undef;
in eval STRING: $VAR1 = '1';
in eval BLOCK: $VAR1 = '1';
[download]

It turns out that $^S doesn't distinguish between BLOCK and STRING eval at all.