Re^3: what is difference between calling the function in Perl/Tk in the following ways

[runrig]

It's the circular reference preventing garbage collection that would cause the leak. The same sort of leak that happens when you repeatedly create anonymous recursive subs like:

my $fact;
$fact = sub {
  my $n = shift;
  return $n if $n <= 1;
  return $n*fact($n-1);
}

Hmm, you're right, the other one would probably leak also if they both contain $button. (update: oops...looking at wrong thread since the OP didn't even have a circular reference in the example).

[ikegami]

the other one would probably leak also if they both contain $button

Exactly.

my $obj;
my $obj = { data => [ \&f, \$obj ] };       # leaks

my $obj;
my $obj = { data => [ sub { f($obj) } ] };  # leaks

my $arg;
my $obj = { data => [ \&f, \$arg ] };       # doesn't leak

my $obj;
my $obj = { data => [ sub { f($arg) } ] };  # doesn't leak