any way to retrieve a circular reference value

Question

I wrote th following program to see feature called circular reference in perl.

my $foo = 100;  
$foo = \$foo;
print "Value of foo is : ", $$foo, " " , $foo;

the output was:

Value of foo is : REF(0x21b632c) REF(0x21b632c)

but i was wondering where the value 100 gone can any one help me.or is it a memory leak?

The value of 100 was clobbered. That is no different than saying, `$f = 100`, and then saying `$f = 'foobar'`. The old value is lost. — Miller, Mar 28 '14 at 09:45
Also, as perl uses a reference-counted garbage collector (plus a mark-and-sweep for circular references), there is no memory leak either. — Phylogenesis, Mar 28 '14 at 09:46
@Phylogenesis It's new for me that Perl does mark-and-sweep – are you confusing this with CPython? OP's code will absolutely leak memory (`$foo` has a refcount of two, and will never drop to zero unless the circle is broken by reassignment or reference weakening). However, the scalar `100` will be garbage-collected. — amon, Mar 28 '14 at 09:54
@amon It seems the mark-and-sweep is only run on exit. See [this question](http://stackoverflow.com/questions/2972021/garbage-collection-in-perl). — Phylogenesis, Mar 28 '14 at 10:05
@Phylogenesis, actually a circular reference *is* a memory leak, because the clean-up doesn't happen until the program exits. — , Mar 28 '14 at 10:21
@dan1111 To be fair, my point about the memory leak was a direct answer to the question about whether the scalar value leaks. — Phylogenesis, Mar 28 '14 at 10:23

score 0 · Answer 1 · answered Mar 29 '14 at 15:33

The value 100 was overwritten. When you assign a value into a variable, it replaces the previous value.

my $foo = 100;
$foo = "a string here";

The value 100 has gone. The same thing happens in your code above. The only difference is what kind of value was put in there.

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