# qr/{,n}/ is now accepted

I find this code very unfortunate, what does it mean if the empty string can be repeated n times?

This could better be either a syntax error. But I'm rather expecting Perl not reading the curlies as metas.

from the delta

An empty lower bound is now accepted for regular expression quantifiers, like {,3}.

so {,3} is the same like {0,3} or {1,3} ?

please elaborate!

edit

to demonstrate my point

  DB<8> $re = qr/{0,3}/

  DB<9> p "" =~ $re

  DB<10> p "{0,3}" =~ $re
1
  DB<11> p $]
5.032001
  DB<12>

  DB<13> use warnings; use strict; my $re = qr/{,3}/

  DB<14>
[download]

the curlies are taken literally!

qr/{,3}/ was always allowed.

what does it mean if the empty string can be repeated n times?

It means "We kept the heading short, feel free to split hairs." The single line below that heading reads: An empty lower bound is now accepted for regular expression quantifiers, like {,3}.

But I'm rather expecting Perl not reading the curlies as metas.

Correct. A open curly was interpreted literally in regular expressions in a lot of places in old Perl versions. Since Perl 5.26 some of these uses were forbidden, and Perl 5.28 made some of these uses non-fatal again. Relevant reading:

• perldelta 5.26: Unescaped literal "{" characters in regular expression patterns are no longer permissible
• perldiag 5.26: Unescaped left brace in regex is illegal here in regex; marked by <-- HERE in m/%s/
• perldelta 5.28: Some uses of unescaped "{" in regexes are no longer fatal

so {,3} is the same like {0,3} or {1,3} ?

Same as {0,3}.

Discussing "very unfortunate" and "bad" code examples is hardly "hair splitting".

We both are experienced enough to handle this, but many others won't.

...documentation can include sloppy wording, that's hard to avoid.

But sloppy code is not a good idea, since there is no doubt of interpretation.

I'll file a perlbug.

Cheers Rolf
_{(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery}

"qr/{,3}/ was always allowed"

Nope.

$ perl -E 'say $]'
5.032001
[download]

$ perl -Mstrict -wE 'my $str = "foobar"; say 1 if $str =~ /[o]{1,2}/'
1
[download]

$ perl -Mstrict -wE 'my $str = "foobar"; say 1 if $str =~ /[o]{,2}/'
Unescaped left brace in regex is illegal here in regex; marked by <-- 
+HERE in m/[o]{ <-- HERE ,2}/ at -e line 1.
[download]



The way forward always starts with a minimal test.

> $str =~ /[o]{,2}/'

missing the point!

Already proven in the post you downvoted (line 13)

Cheers Rolf
_{(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery}