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Pre-RFC: “helpcodes” feature

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Felipe Gasper
June 7, 2022 16:55
Pre-RFC: “helpcodes” feature
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> On Jun 3, 2022, at 16:22, Neil Bowers <> wrote:
> Hi Felipe,
> We discussed part 1 – improving the wording of the wide character messages – and agreed that we’d like to see this, and also that it doesn’t need to go via an RFC.
> So we encourage you to propose some wording on p5p, and then submit a PR.
> We’ve marked your Pre-RFC as "N/A" in the tracker. You could start a separate Pre-RFC thread if you want to raise the idea of codes for warnings and error messages.

Some further thoughts:

Changing the wording of the error message as it stands risks breaking preexisting applications. So it seems imprudent to do it without a feature/pragma.

Even that aside, the broader issue is that Perl’s warnings & error messages can gainfully be made more helpful. Making one change specifically for wide-character warnings seems less-good than looking at whether we might be able to improve the whole lot.

And so, here’s a proposal:


# This tells Perl to prefix all of its “native” warnings & exceptions with a
# “help code”. It will also cause various tweaks to the messages.
use feature 'helpcodes';

# This normally warns `Wide character in print …`.
# Under the helpcodes feature it will instead warn (note the updated text):
#    HELP-WIDEOUT: Wide character in print (remember to encode!) …`
print "\x{100}";

# This normally dies `Illegal division by zero …`.
# Under the helpcodes feature it will instead die thus:
#    HELP-DIVZERO: Illegal division by zero …`
my $foo = 9 / 0;


The idea is simple: apply the familiar pattern of POSIX error names (ENOENT, EPERM, etc.) to Perl. These will be easily searchable in search engines, and we can list them in something like perlhelpcodes.pod.



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