Please reread what I wrote. I agreed that the memory used directly by the lexical will not be freed. But I wanted to clarify that in many cases this doesn't matter much. For example:

sub foo
{
    my $val;
    if(  @_  ) {
        $val= shift;
    } else {
        undef $val;
    }
    return $val;
}
foo( "x" x 10_000 );
# 10,000 bytes of memory still tied up
foo()
# those 10,000 bytes now free to be reused
foo( \( "x" x 10_000 ) );
# the few bytes needed to store a reference still tied up,
# but the 10,000 bytes for the string value itself are
# already free to be reused.
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Yes, closures never being freed is a bug due to Perl itself making a circular reference. I believe this has already been fixed. Your example code should not leak memory whether you consider it reasonable for that to happen or not. (: