Surprised that $^N action works if string is global, fails if string is local

[p5pRT]

Migrated from rt.perl.org#37543 (status was 'resolved')

Searchable as RT37543$

[p5pRT]

From [email protected]

Created by [email protected]

Surprised that $^N does not work on local (my) variable in a sub but
instead
requires a global variable. Following code works OK since '$foundstr'
is global, but
remove '#' (making the $foundstr variable local to sub) and code
crashes​:

#START OF CODE
&findABC('abcd');
&findABC('abcd'); # 2nd call should yield identical results

sub findABC
{
  my $txt = shift;
  # my ($foundstr); # uncomment this statement to see problem

  if ($txt =~
  m/
  (ABC) (?{$foundstr = $^N})
  /ix
  )
  {
  printf "after regex \$foundstr = '$foundstr'\n";
  };
  }

# END OF CODE

# EXAMPLE OUTPUT​:
Case 1) with global $foundstr​:

after regex $foundstr = 'abc'
after regex $foundstr = 'abc'

Case 2) with "my $foundstr;" statement added to sub​:

after regex $foundstr = 'abc'
Use of uninitialized value in concatenation (.) or string at problem.pl
line 15.

after regex $foundstr = ''

# END OF EXAMPLE OUTPUT

Perl Info

Flags:
    category=core
    severity=medium

Site configuration information for perl v5.8.7:

Configured by builder at Mon Jun  6 13:36:05 2005.

Summary of my perl5 (revision 5 version 8 subversion 7) configuration:
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    Less verbose ExtUtils::Install and Pod::Find
    instmodsh upgraded from ExtUtils-MakeMaker-6.25
    24699 ICMP_UNREACHABLE handling in Net::Ping
    21540 Fix backward-compatibility issues in if.pm


@INC for perl v5.8.7:
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Systems\MPEG;H:\Program Files\Ulead\Ulead DVD MovieFactory 3
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[p5pRT]

From [email protected]

On Oct 26, via RT and UNEXPECTED_DATA_AFTERdevanney@​prodigy.netsaid​:

Surprised that $^N does not work on local (my) variable in a sub but
instead
requires a global variable. Following code works OK since '$foundstr'
is global, but
remove '#' (making the $foundstr variable local to sub) and code
crashes​:

It's not that $^N doesn't work. It's that (?{ $foundstr = $^N }) ends up
being a closure around the lexical $foundstr. This is a known bug. The
first time the regex is compiled, the (?{ ... }) refers to a specific
lexical. Subsequent calls to the regex will still be operating on that
first lexical.

   printf "after regex \\$foundstr = '$foundstr'\\n";

Don't use printf() unless you mean "print a formatted string".

--
Jeff "japhy" Pinyan % How can we ever be the sold short or
RPI Acacia Brother #734 % the cheated, we who for every service
http​://www.perlmonks.org/ % have long ago been overpaid?
http​://princeton.pm.org/ % -- Meister Eckhart

[p5pRT]

The RT System itself - Status changed from 'new' to 'open'

[p5pRT]

From [email protected]

thanks very much...

"japhy@​perlmonk.org via RT" wrote​:

On Oct 26, via RT and UNEXPECTED_DATA_AFTERdevanney@​prodigy.netsaid​:

Surprised that $^N does not work on local (my) variable in a sub but
instead
requires a global variable. Following code works OK since '$foundstr'
is global, but
remove '#' (making the $foundstr variable local to sub) and code
crashes​:

It's not that $^N doesn't work. It's that (?{ $foundstr = $^N }) ends up
being a closure around the lexical $foundstr. This is a known bug. The
first time the regex is compiled, the (?{ ... }) refers to a specific
lexical. Subsequent calls to the regex will still be operating on that
first lexical.

   printf "after regex \\$foundstr = '$foundstr'\\n";

Don't use printf() unless you mean "print a formatted string".

--
Jeff "japhy" Pinyan % How can we ever be the sold short or
RPI Acacia Brother #734 % the cheated, we who for every service
http​://www.perlmonks.org/ % have long ago been overpaid?
http​://princeton.pm.org/ % -- Meister Eckhart

[p5pRT]

From @cpansprout

This has been fixed by the commits leading up to eb58a7e.

[p5pRT]

@cpansprout - Status changed from 'open' to 'resolved'