overloading and formats (was Re: [perl #55668] 'eval'ing a certain format string segfaults perl)

formats consume their variables:

$ cat eat.pl
#!perl -w

$a = <<'EOT';
Pie
Good
EOT

print $a;
print "...\n";

formline '^*', $a;

print $a;
__END__
$ perl eat.pl 
Pie
Good
...
Good


What should the output of this be?

$ cat eat_overload.pl
#!perl -w
use strict;
package Pie;
use overload '""' => sub { return <<'EOT';
Pie
Good
EOT
};

sub new {
  bless [], shift;
}

package main;

$a = Pie->new;

print $a;
print "...\n";

formline '^*', $a;

print $a;
__END__


[No, I'm not going to give any clues. The current implementation is wrong, and
I don't know what the right answer is. Should the string return from an
overloaded reference be treated as a read only value?]

Nicholas Clark

• [perl #55668] 'eval'ing a certain format string segfaults perl by Arthur Kantor
• Re: [perl #55668] 'eval'ing a certain format string segfaults perl by Alexandr Ciornii
• Re: [perl #55668] 'eval'ing a certain format string segfaults perl by Nicholas Clark
• overloading and formats (was Re: [perl #55668] 'eval'ing a certain format string segfaults perl) by Nicholas Clark