Each on anonymous hash is causing endless loop.

LanX has asked for the wisdom of the Perl Monks concerning the following question:

ehm ... I just stumbled over a strange effect when using each on an anonymous hash.

Bug or feature?

C:\>perl
my $hr = {a=>1,b=>2};
$\="\n";
while ( my ($k,$v) = each %{ $hr } ) { print qq($k => $v) }
__END__
b => 2
a => 1

C:\>perl
$\="\n";
$x=10; 
while ( my ($k,$v) = each %{ {a=>1,b=>2} } ) { print qq($k => $v); die
+ "abort" unless $x-- }
__END__
b => 2
b => 2
a => 1
b => 2
a => 1
a => 1
b => 2
b => 2
a => 1
a => 1
a => 1
abort at - line 2.

C:\>perl -E"say $]"
5.032001
[download]

Cheers Rolf
_{(addicted to the Perl Programming Language :)

Wikisyntax for the Monastery}

Comment on Each on anonymous hash is causing endless loop. Download Code

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Re: Each on anonymous hash is causing endless loop. by tybalt89 (Monsignor) on Aug 24, 2022 at 21:14 UTC
Why strange? It's a new hash every iteration. This is expected behavior.	[reply]
Re^2: Each on anonymous hash is causing endless loop. by LanX (Saint) on Aug 24, 2022 at 21:22 UTC
Thanks, good explanation! I was expecting some kind of constant folding ... `C:\>perl -M5.012 my $x = 5; while ( say {a=>1,b=>2} ) { die "abort" unless --$x } __END__ HASH(0xf5b3d0) HASH(0xf5b508) HASH(0xf5b3d0) HASH(0xf5b508) HASH(0xf5b3d0) abort at - line 2. C:\>` [download] Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l]
Re: Each on anonymous hash is causing endless loop. by choroba (Cardinal) on Aug 24, 2022 at 20:57 UTC
`say while $_ = shift @{ [1 .. 10] }; # Never stops, either.` [download] `map{substr$_->[0],$_->[1]\|\|0,1}[\\|\|{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^ARGV,3]`	[reply] [d/l] [select]