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