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Re: Perl 5.16 and Beyond.

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From:
Dave Mitchell
Date:
September 14, 2011 03:36
Subject:
Re: Perl 5.16 and Beyond.
Message ID:
20110914102811.GG8619@iabyn.com
On Tue, Sep 13, 2011 at 08:33:09PM +0200, Johan Vromans wrote:
> Actually, I see more significant problems with Perl trying to carry all
> old semantics into all new versions. You cannot simpy make a small
> change to a built-in, you have to make a backup copy and keep it just in
> case. This is a potential maintenance nightmare.

+10

I think the devil is in the detail. If, while running under 5.20,

    use v5.16;

is just about equivalent to

    no feature 'list of features added in 5.18, 5.20';

then I'd be happy with that.

If it's supposed to mean "this code will run in exactly the same way as if
you have just applied the perl-5.16.0 executable against it", then I will
run away screaming.

So... do we backwardly support bug fixes where the bug fix caused a
visible change in behaviour? Even where the old behaviour was clearly wrong
and went against the documented behaviour?

Or... in my current work to fix the mess that is /(?{...})/, should
'use v5.14' cause this code:

    /(?{ warn "boo" })/

to output the old-style message

    boo at (re_eval 1) line 1.

rather than the new style

    boo at file line N.

(where the change in message is an artifact of the fact that (?{...}) is
parsed in a completely different way now).

Etc etc...


-- 
But Pity stayed his hand. "It's a pity I've run out of bullets",
he thought. -- "Bored of the Rings"

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