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Re: RFC: New regex modifier flags

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David Golden
August 4, 2010 06:56
Re: RFC: New regex modifier flags
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On Wed, Aug 4, 2010 at 9:12 AM, Jesse Vincent <> wrote:
>> I would suggest we reconsider whether this is really a "deprecation"
>> situation.  Is there any documentation that states that such
>> constructs are legal?  I was surprised to find that they are. I would
>> have expected it to be a syntax error.  If we instead "fix the bug"
>> that invalid regex flags are not detected as a syntax error, then we
>> don't have to consider this a deprecated feature and we don't have to
>> wait two years for a sane approach.  That may lead us to favor
>> different options.
> "Not documented" isn't really a great metric for "is fine to break
> without notice" unless we turn it on with the 5.14 pragma.

That's not what I meant.  I'm saying that another valid interpretation
is that it is a bug in the parser that Perl doesn't flag a "run-on"
between regex modifiers and certain keywords as a syntax error.

Of course, we can debate whether it's a bug or a feature.  But I feel
that the default assumption so far has been "feature" and that we
follow the "can't be removed without a deprecation cycle" policy.  I'm
calling the question of whether this is a bug, and I believe the
standing policy is that we don't have to be backwards compatible with

If we had this debate before regex modifiers were ever introduced, I'm
pretty confident the view would be that it's a bad idea to allow a
run-on precisely because it closes out the extensibility of future
regex modifiers (not to mention being just generally confusing).
Thus, I think the behavior is a bug, not a feature.

I was asking about documentation to see if there is any evidence to
the contrary that would suggest this behavior was intentional design.

-- David

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