B::Hooks::OP::Check::StashChange allows one to run a callback whenever the current package changes during compilation. If a hook is installed, all subsequent calls to split appear to be removed. How is this possible?

Here's some code without a hook being installed:

INSTALL_HOOK=0 perl -MO=Deparse -MB::Hooks::OP::Check::StashChange -e 
+'BEGIN { my $id = B::Hooks::OP::Check::StashChange::register(sub {}) 
+if $ENV{INSTALL_HOOK}; } print split "x", "1x2"'

use B::Hooks::OP::Check::StashChange;
sub BEGIN {
    my $id = B::Hooks::OP::Check::StashChange::register(sub {
        
    }
    ) if $ENV{'INSTALL_HOOK'};
}
print split(/x/, '1x2', 0);
-e syntax OK
[download]

and here's the same code with the hook enabled:

INSTALL_HOOK=1 perl -MO=Deparse -MB::Hooks::OP::Check::StashChange -e 
+'BEGIN { my $id = B::Hooks::OP::Check::StashChange::register(sub {}) 
+if $ENV{INSTALL_HOOK}; } print split "x", "1x2"'

use B::Hooks::OP::Check::StashChange;
sub BEGIN {
    my $id = B::Hooks::OP::Check::StashChange::register(sub {
        
    }
    ) if $ENV{'INSTALL_HOOK'};
}
print 'x', '1x2';
-e syntax OK
[download]

As you can see, "split" disappeared and it's arguments are simply being printed. The module code itself is pretty short but given my lack of experience with XS I can't pinpoint the issue. How can a builtin get disabled like this?

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