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"$VAR1" is an artifact of how Data::Dumper would generate code
using its "Purity" feature.
Data::Dumper::Interp simply passes through these annotations.

However with I<Refaddr(true)>, multiple references to the same thing
will all show the address of the referenced thing.

=item threads::shared support

When the address of a shared variable is shown
(e.d. when the B<Refaddr> option is enabled or if calling B<addrvis()>),
the variable's I<globally unique ID> shown instead of the C<refaddr>.

(The C<refaddr> of a shared variable is misleading; it refers
to a thread-local intermediary and may be different in
each thread even though the same shared object is being referenced).

Relatedly, the C<$VAR> references in default Data::Dumper output are
generally incorrect when shared variables are involved because Data::Dumper
uses only C<refaddr> values to identify refs to the same item.
Enabling I<Refaddr(true)> will show linkage correctly, albiet in a different way.

=item The special "_" stat filehandle may not be preserved

Data::Dumper::Interp queries the operating
system for the window size to initialize C<$Foldwidth>, if it
is not already defined; this may change the "_" filehandle.
After the first call (or if you pre-set C<$Foldwidth>),
the "_" filehandle will not change across calls.

=back

=head1 DIFFERENCES FROM Data::Dumper

Results differ from plain C<Data::Dumper> output in the following ways
(most of these can be controlled via Config options):

=over 2

=item *

Punctuation variables such as $@, $!, and $?, are preserved over calls.

=item *

A final newline is I<never> included.

Everything is shown on a single line if possible, otherwise wrapped to
your terminal width (or C<$Foldwidth>), with indented structure levels.

=item *

Printable Unicode characters appear as themselves instead of \x{ABCD}.

Note: If your data contains 'wide characters', you should
C<< use open IO => ':locale'; >> or otherwise arrange to
encode the output for your terminal.
You'll also want C<< use utf8; >> if your Perl source is written
using utf8 characters outside the ASCII range.

Undecoded binary octets (e.g. data read from a 'binmode' file)
will still be escaped as individual bytes.

=item *

Depending on options, spaces·may·be·shown·visibly
and '␤' may be shown for newline (and similarly for other ASCII controls).

"White space" characters in qr/compiled regex/ are shown as \t, \n etc.

=item *

CODE refs show the name of the referenced sub using L<Sub::Identify>
instead of C<sub{ "DUMMY" }>.  If the sub is anonymous, the file:lineno
where it was defined is shown.

=item *

The internals of objects are not shown by default.

If stringifcation is overloaded it is used to obtain the object's
representation.  For example, C<bignum> and C<bigrat> numbers are shown as easily
readable values rather than S<"bless( {...}, 'Math::...')">.

Stingified objects are prefixed with "(classname)" to make clear what
happened.

The "virtual" value of objects which overload a dereference operator
(C<@{}> or C<%{}>) is displayed instead of the object's internals.

=item *

Hash keys are sorted treating numeric "components" numerically.
For example "A.20" sorts before "A.100".

=item *

Numbers and strings which look like numbers are kept distinct when displayed,
i.e. "0" does not become 0 or vice-versa. Floating-point values are shown
as numbers not 'quoted strings'.

Although such differences might be immaterial to Perl during execution,
they may be important when communicating to a human.

=item *

References to shared variables (see L<threads::shared>) are shown correctly
with the C<Refaddr> feature.  Data::Dumper's C<$VAR> expressions are usually
incorrect when shared variables are involved.

=back

=head1 SEE ALSO

Data::Dumper

=head1 AUTHOR

Jim Avera  (jim.avera AT gmail)

=head1 LICENSE