Where is Perl's default object-to-string conversion defined?

Question

If I print a reference to a blessed object in Perl, I get something like this:

Foo::Bar=HASH(0x0123456789ab)

Where is that code defined? The first part is ref($obj), but where does the HASH hex value come from?

I'm attempting to write a to_string overloaded operator for objects that have an optional name attribute. If the name is provided, I'd like it to print

Foo::Bar(name=joe)

and fall back to the default Perl string if not name is undefined. So I either have to be able to invoke Perl's conversion code from my code, or write the equivalent myself, hence my question.

Answer 1

I don't believe the format is documented, but it's unlikely to change. It's equivalent to

use Scalar::Util qw( blessed refaddr reftype );

my $pkg = blessed($ref);
my $str = sprintf("%s%s(0x%x)",
   ( defined($pkg) ? "$pkg=" : "" ),
   reftype($ref),
   refaddr($ref),
);

You can use blessed, reftype and refaddr if you want the components of Perl's stringification of a reference, but the following is the best way to obtain Perl's stringification of a reference:

use overload qw( );

my $str = overload::StrVal($ref);

Answer 2

Never mind, of course the minute after I post this, I find the answer:

overload::StrVal($o)

(see also Stop perl overloading or print memory "address" of reference)