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lib/Devel/DebugHooks.pm  view on Meta::CPAN

Before: SCALAR(0x134d398) <<SCALAR(0x134d398) 7
After: SCALAR(0x1239bc8) <<SCALAR(0x134d398) 7

We see that in *first* example the new variable is created: The new address of $DB::single is SCALAR(0x110cbc8)
but when assigning to $DB::single the value by old reference (SCALAR(0x10f8310) changed too.
In *second* example we see that addressing works in same manner, but value 7 is preserved as expected.

Why the value of $DB::single is not preserved?

	# my $y =  \$DB::single;
	# # Can not use weaken. See error at 'reports/readline' file
	# use Scalar::Util 'weaken';
	# weaken $y;
	# Because of $DB::single magic we can not access to old value by reference
	# The localization is broken if we save a reference to $DB::single
	# {
	# 	my $x =  $DB::single;
	# 	print "Before: ". \$DB::single ." <<$DB::single $x >$y $$y\n"; # $$x == 0
	# 	local $DB::single =  $DB::single +1;
	# 	print "After: ". \$DB::single ." <<$DB::single $x >$y $$y\n";  # $$x == 1, not 0
	# }
	# print "OUT: ". \$DB::single ." <<$DB::single - $x - $$x >$y\n";