The only way I see is saving the typeglob, destroying it and re-creating it with all but the CODE slot:
use 5.010; use strict; our $FOO; BEGIN { $FOO = 'still foo'; } sub FOO () { 'foo' } BEGIN { *BAR = *FOO; say "in BEGIN (1): \$FOO = '$FOO'"; undef *FOO; say "in BEGIN (2): \$FOO = '$FOO'"; *FOO = *BAR{SCALAR}; undef *BAR; } say defined &FOO ? 'subroutine defined' : 'subroutine undef'; say eval 'my $false; FOO if $false; 1' ? 'FOO allowed' : 'FOO not allowed' ; say $FOO; __END__ in BEGIN (1): $FOO = 'still foo' in BEGIN (2): $FOO = '' subroutine undef FOO not allowed still foo

update: tweaked the code to more closely resemble the OP's.

--shmem

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

In reply to Re: Removing CODE slot in typeglob / Reversing "use subs ...;" by shmem
in thread Removing CODE slot in typeglob / Reversing "use subs ...;" by lodin

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