require Data::Dumper if $^P;

#...lots of code...

my %output; ### The information that was output last
my %current; ### The current record's information
my %previous; ### The previous record's information

### Now that these variables are in scope, create a closure
### that we can use for debugging. This prints all 3 stacks.
	
my $stack = sub {
	print Data::Dumper->Dump(
		[\%previous, \%output, \%current],
		['*previous', '*output', '*current']
	);
};