modifying within a perl5 block

[Richard Hainsworth]

Dear Audrey,

Consider:
my $x = 'test';
{
use v5;
$x .= 'ing';
};
say $x;

pugs yields 'test'
and not 'testing' - as expected.

Moreover, the following hangs pugs:

my $x = 'test';
my $y = 'case';
{
use v5;
$x .= 'ing';
{
use v6-alpha;
$y ~= 'book';
};
};
say $x;
say $y;

I have committed a test to t/perl5, viz., modify_inside_p5.t (which runs
but fails)
and I attach another. viz., modify_inside_p5_p6.t , which hangs pugs.

Regards,
Richard