Using 

#!/usr/bin/perl

use strict;
use warnings;

use v5.36;

say 'Hello, world!';

[download]

In 5.38, we see: 

  DB<1> use Devel::Peek;

  DB<2> Dump( ${"_<a.pl"}[8] );
SV = PVMG(0x55d8627958e0) at 0x55d86251ff80
  REFCNT = 1
  FLAGS = (IOK,POK,IsCOW,pIOK,pPOK)
  IV = 94387850872920
  NV = 0
  PV = 0x55d8628074b0 "say 'Hello, world!';\n"\0
  CUR = 21
  LEN = 32
  COW_REFCNT = 1

  DB<3> Dump( ${"_<a.pl"}[6] );
SV = PVMG(0x55d862786d50) at 0x55d86251fec0
  REFCNT = 1
  FLAGS = (POK,pIOK,pNOK,pPOK)
  IV = 0
  NV = 0
  PV = 0x55d8627d7d50 "use v5.36;\n"\0
  CUR = 11
  LEN = 16

[download]

See how "line 8" has IOK and POK, but "line 6" only has POK? That means that line 8 contains an integer in addition to the string, while line 6 contains only the string. This doesn't match the documentation.

(As a side note, why 94387850872920? In hex, it's 55D862528858, which in the same range as the addresses being dumped. So it looks like it's not just a flag, but a pointer to something.)

Note that the problem is limited to lines containing pragmas. The non-pragma unbreakable lines have IOK and a value of zero. 

  DB<4> use Devel::Peek;Dump( ${"_<a.pl"}[5] );
SV = PVMG(0x55856a4198d0) at 0x55856a4e9630
  REFCNT = 1
  FLAGS = (IOK,POK,pIOK,pPOK)
  IV = 0
  NV = 0
  PV = 0x55856a486840 "\n"\0
  CUR = 1
  LEN = 16

[download]

So only the lines with pragmas are broken. But this wasn't always the case. They used to be broken in a different way. Here with 5.34, we see that pragmas were once breakable. 

  DB<2> Dump( ${"_<a.pl"}[6] );
SV = PVMG(0x55874ddaf680) at 0x55874db508a8
  REFCNT = 1
  FLAGS = (IOK,POK,pIOK,pPOK)
  IV = 94039612799016
  NV = 0
  PV = 0x55874db739a0 "use v5.10;\n"\0
  CUR = 11
  LEN = 16

[download]

I'm guessing that when they fixed the bug marking pragmas as breakable, they forgot to set the IOK flag.

Bug report

In reply to Re: Perl 5.36 warns for magic comparison by ikegami
in thread Perl 5.36 warns for magic comparison by hurricup

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