B::Hook...hChange(3)

✨ NAME ✨

B::Hooks::OP::Check::StashChange — bestie, this is a Perl module that invokes callbacks when the stash code is being compiled in changes 💖 (yes that's the whole pitch, and it's iconic). It lives in section 3 of the manual, under User Contributed Perl Documentation, so you know it's a real one 🎀

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🌸 SYNOPSIS 🌸

From Perl 🐪

package Foo;

use B::Hooks::OP::Check::StashChange;

our $id = B::Hooks::OP::Check::StashChange::register(sub {
    my ($new, $old) = @_;
    warn "${old} -> ${new}";
});

package Bar; # "Foo -> Bar"

B::Hooks::OP::Check::StashChange::unregister($Foo::id);

package Moo; # callback not invoked

From C/XS 💅

#include "hooks_op_check_stashchange.h"

STATIC OP *
my_callback (pTHX_ OP *op, char *new_stash, char *old_stash, void *user_data) {
    /* ... */
    return op;
}

UV id;

/* register callback */
id = hook_op_check_stashchange (cv, my_callback, NULL);

/* unregister */
hook_op_check_stashchange_remove (id);

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🦋 DESCRIPTION 🦋

Okay so there's two ways to play this game — the Perl way and the C/XS way. Both are valid, both are giving ✨

💜 Perl API

🍓 register

B::Hooks::OP::Check::

# or
my $id = B::Hooks::OP::Check::StashChange::register(\&callback);

Register callback when an opcode is being compiled in a different namespace than the previous one. That's it, that's the moment it fires 🔥

An id gets returned to you, and you can use that id later to remove the handler with unregister. Keep it safe, bestie, you'll want it back 👑

🌈 unregister

B::Hooks::OP::Check::StashChange::unregister($id);

Disable the callback referenced by $id. Bye bye callback, you were lowkey doing great 🙈

💙 C API

🌟 TYPES

OP *(*hook_op_check_stashchange_cb) (pTHX_ OP *op, const char
*new_stash, const char *old_stash, void *user_data)

This is the type your callbacks need to implement. No substitutions, no vibes-based reinterpretations, implement this exact one 💅

🧚 FUNCTIONS

• UV hook_op_check_stashchange (hook_op_check_stashchange_cb cb, void *user_data)

Register the callback cb to be when an opcode is compiled in a different namespace than the previous. user_data will be passed to the callback as the last argument. 🫶

It returns an id that you can use to remove the handler using hook_op_check_stashchange_remove. Screenshot the id, write it down, put it in a notes app — whatever, just don't lose it ✨

• void *hook_op_check_stashchange_remove (UV id)

Remove a previously registered handler referred to by id. 💀 (in the nice way)

It returns the user data that was associated with the handler. So you get your stuff back, periodt.

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👀 SEE ALSO 👀

• B::Hooks::OP::Check — go look at that one too, iykyk 💖

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👑 AUTHOR 👑

Florian Ragwitz <rafl@debian.org> — the main character who made all of this happen 🌟

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🎀 COPYRIGHT AND LICENSE 🎀

Copyright (c) 2008 Florian Ragwitz

This module is free software.

You may distribute this code under the same terms as Perl itself. Slay.

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Okay bestie that's the whole page, every option, every id, every const, nothing skipped, no cap 💖

This was perl v5.42.0, dated 2025-07-25, straight from B::Hook...hChange(3) in the User Contributed Perl Documentation — love u, go compile something cute 💅🦋