Re: Seeking clarification on possible bug in regex using \G and /gc

I'm not able to reproduce the behaviour you describe. Tried in 5.18.2 and 5.27.7, code:

#! /usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

{
    local $_ = 'foo';
    say '1 Start' if /\G foo/gcx;
    say '1 Mid'   if /\G .*/gcx;
    say '1 End'   if /\G \z/gcx;
}

{
    local $_ = 'foo';
    say '2 Start' if /\G foo/gcx;
    say '2 Mid'   if /\G .+/gcx;
    say '2 End'   if /\G \z/gcx;
}
[download]

Output:

1 Start
1 Mid
2 Start
2 End
[download]

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
[download]

Comment on Re: Seeking clarification on possible bug in regex using \G and /gc Select or Download Code

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Re^2: Seeking clarification on possible bug in regex using \G and /gc by davido (Cardinal) on Mar 15, 2018 at 01:45 UTC
Thanks choroba for setting me straight. If there's one thing that I keep forgetting to learn it's not to post regex questions or answers in haste. ;) You are correct. This: `local $_ = 'foo'; m/\Gfoo/gc && say 'Matched foo'; m/\G.+/gc && say 'Matched dot star'; m/\G\z/gc && say 'Matched end of string';` [download] ...produces this: `Matched foo Matched end of string` [download] And this: `local $_ = 'foo'; m/\Gfoo/gc && say 'Matched foo'; m/\G./gc && say 'Matched dot star'; m/\G\z/gc && say 'Matched end of string';` [download] ...produces this: `Matched foo Matched dot star` [download] ...indicating that end of string was consumed by dot star, though it's still a little odd because this also matches: `local $_ = 'foo'; m/\Gfoo/gc && say 'Matched foo'; m/\G.\z/gc && say 'Matched dot star and end of string';` [download] ...produces this: `Matched foo Matched dot star and end of string` [download] So while it may be eluded to in the documentation it's not entirely unsurprising. :) Dave	[reply] [d/l] [select]
Re^2: Seeking clarification on possible bug in regex using \G and /gc by Rhandom (Curate) on Mar 14, 2018 at 23:24 UTC
Breaks for me on perl 5.26. `perl -E 'local $_ = "foo"; say "Start" if /\G foo/gcx; say "Mid" if /\ +G ./gcx; say "End" if /\G \z/gcx' Start Mid` [download] Should instead print `Start Mid End` [download] Here is a more extended item looking at pos as well. `perl -E 'local $_ = "foo"; say "Start" if /\G foo/gcx; say pos; say "M +id" if /\G ./gcx; say pos; say "End" if /\G \z/gcx; say "At End" if +pos == length' Start 3 Mid 3 At End` [download] my @a=qw(random brilliant braindead); print $a[rand(@a)];	[reply] [d/l] [select]
Re^3: Seeking clarification on possible bug in regex using \G and /gc by choroba (Cardinal) on Mar 14, 2018 at 23:52 UTC
> Should instead print Why? Using `perl -Mre=debug` will show you your mistake: `... Matching REx "\G \z" against "" 3 <foo> <> \| 1:GPOS(2) 3 <foo> <> \| 2:EOS(3) 3 <foo> <> \| 3:END(0) Match possible, but length=0 is smaller than requested=1, failing! Match failed` [download] The length=1 request comes from the previously mentioned Repeated Patterns Matching a Zero-length Substring: The higher-level loops preserve an additional state between iterations: whether the last match was zero-length. To break the loop, the following match after a zero-length match is prohibited to have a length of zero. ($q=q:Sq=~/;[c](.)(.)/;chr(-\|\|-\|5+lengthSq)`"S\|oS2"`map{chr \|+ord }map{substrSq`S_+\|`\|}3E\|-\|`7**2-3:)=~y+S\|`+$1,++print+eval$q,q,a, [download]	[reply] [d/l] [select]