Question

What syntax, if any, is able to take a reference of a builtin like shift?

$shift_ref = $your_magic_syntax_here;

The same way you could to a user defined sub:

sub test { ... }

$test_ref = \&test;

I’ve tried the following, which all don’t work:

\&shift
\&CORE::shift
\&{'shift'}
\&{'CORE::shift'}

Your answer can include XS if needed, but I’d prefer not.

Clarification: I am looking for a general purpose solution that can obtain a fully functional code reference from any builtin. This coderef could then be passed to any higher order function, just like a reference to a user defined sub. It seems to be the consensus so far that this is not possible, anyone care to disagree?

Answer 1

No, you can’t. What is the underlying problem you are trying to solve? There may be some way to do whatever that is.

Re the added part of the question “Your answer can include XS if needed, but I’d prefer not.”,
calling builtins from XS is really hard, since the builtins are set up to assume they are running as part of a compiled optree and have some global variables set. Usually it’s much easier to call some underlying function that the builtin itself uses, though there isn’t always such a function, so you see things like:

buffer = sv_2mortal(newSVpvf("(caller(%d))[3]", (int) frame));
caller = eval_pv(SvPV_nolen(buffer), 1);

(doing a string eval from XS rather than go through the hoops required to directly call pp_caller).