Re^7: about style: use possessive or atomic?

I get the same warning with Strawberry Perl v5.20.2, but not on v5.18.2.

You're right! My default perl is currently 5.18:

C:\test>\perl5.18\perl\bin\perl.exe junk37.pl
SUCCESS
SUCCESS
SUCCESS
SUCCESS
SUCCESS

C:\test>\Perl5.20\bin\perl.exe junk37.pl
Useless use of greediness modifier '+' in regex; marked by <-- HERE in
+ m/((?:a|b)){1}+ <-- HERE / at junk37.pl line 15, <DATA> line 2.
SUCCESS
SUCCESS
SUCCESS
SUCCESS
SUCCESS

C:\test>\Perl22\bin\perl.exe junk37.pl
Useless use of greediness modifier '+' in regex; marked by <-- HERE in
+ m/((?:a|b)){1}+ <-- HERE / at junk37.pl line 15, <DATA> line 2.
SUCCESS
SUCCESS
SUCCESS
SUCCESS
SUCCESS
[download]

Is the warning erroneous?

Erm. I was relying on Perl to tell me :)

The fact that the warning has been recently added suggests it is probably correct.

That said, the construct is still listed in the 5.22 docs: {n}+ Match exactly n times and give nothing back (redundant); which basically means your guess is as good as anybody's at this point?

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority". I knew I was on the right track :)

In the absence of evidence, opinion is indistinguishable from prejudice.

I'm with torvalds on this Agile (and TDD) debunked I told'em LLVM was the way to go. But did they listen!

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Re^8: about style: use possessive or atomic?
by Athanasius (Archbishop) on Aug 16, 2015 at 14:13 UTC

From perl5200delta#Diagnostics:

New Warnings
...

Useless use of greediness modifier
This fixes [Perl #42957].

That links to perldiag which has:

Useless use of greediness modifier '%c' in regex; marked by <-- HERE in m/%s/
(W regexp) You specified something like these:
1.  qr/a{3}?/
2.  qr/b{1,1}+/
[download]
The "?" and "+" don't have any effect, as they modify whether to match more or fewer when there is a choice, and by specifying to match exactly a given numer (sic), there is no room left for a choice.

I’m guessing that’s why the qualification “(redundant)” has been added to the entries for {n}? and {n}+ in perlre#Regular-Expressions?

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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Re^9: about style: use possessive or atomic?

by stevieb (Canon) on Aug 16, 2015 at 15:20 UTC

That absolutely makes sense, and I like when warnings like this get added. Any time someone can be warned whenever they are trying to use something useless is another tool that will potentially help someone who's trying to debug something they don't understand: "I'm using a quantifier, but why the heck isn't it working!".

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