tsvars(
   a => my $a = 'A',
   b => my $b = 'B',
);

tsvars(
   a => my $a2,
   b => my $b2 = 'B2',
);

##</code><code>##

my ($ident, $value) = @_[0,1];
tie( $_[1], 'MyTest::Scalar', $ident );
$_[1] = $value if defined($value);
splice(@_, 0, 2);

##</code><code>##

use Data::Alias qw( alias );

my ($ident, $value) = @_[0,1];
alias $_[1] = $VALUES{ $ident );
$_[1] = $value if defined($value);
splice(@_, 0, 2);