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Re: [perl #114178] di/ds/ig exempt from warnings in void context

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Karl Williamson
July 18, 2012 12:46
Re: [perl #114178] di/ds/ig exempt from warnings in void context
Message ID:
On 07/18/2012 12:40 PM, Jesse Luehrs wrote:
> On Wed, Jul 18, 2012 at 09:38:37PM +0300, Leon Timmermans wrote:
>> On Wed, Jul 18, 2012 at 4:35 PM, Paul Johnson <> wrote:
>>> On Tue, Jul 17, 2012 at 11:44:35PM -0700, wrote:
>>>> % perl -we '"qwertasd"'
>>>> Useless use of a constant ("qwertasd") in void context at -e line 1.
>>>> % perl -we '"dsatrewq"'
>>>> Any string starting with "di", "ds", or "ig" is exempt from "void context"
>>>> warnings. I can't find any documentation for this misfeature. It should be
>>>> removed from the interpreter.
>>> It's not really a misfeature.  It's more of an old feature.  The code
>>> explains why it's there:
>>> op.c:1473
>>>                    /* perl4's way of mixing documentation and code
>>>                       (before the invention of POD) was based on a
>>>                       trick to mix nroff and perl code. The trick was
>>>                       built upon these three nroff macros being used in
>>>                       void context. The pink camel has the details in
>>>                       the script wrapman near page 319. */
>>> As far as documentation is concerned, I suppose that it wouldn't be a
>>> bad thing to make a note of this somewhere.
>>> As far as removing it is concerned, I presume that no one is writing new
>>> code in this way, and probably hasn't for a few years.  So the removal
>>> is a trade-off between a slight standardisation and simplification and
>>> breaking backwards compatibility with some perl4 era programs.
>>> I would side with keeping backwards compatibility.
>> Considering this is a warning that has to be enabled explicitly, and
>> that we're talking about perl 4 compatibility here, I wouldn't care
>> too much about such a minor break of backwards compatibility. I'd be
>> surprised if this was the first time in the past 18 years that such a
>> thing happened.
> +1
> -doy


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