Hi all,

i wrote this:

#!/usr/bin/env perl

use strict;
use warnings;
use threads;
use MCE::Loop;
use MCE::Shared;
use LWP::Simple;
use feature qw(say);
use constant AMOUNT => 0;

my $result = MCE::Shared->hash;
my @urls   = qw(http://perlmonks.org http://www.whitehouse.org );

MCE::Loop::init {
    max_workers => 'auto',
    chunk_size  => 1
};

my $fetch = sub { head(shift) };

mce_loop {
    my @data = $fetch->($_);
    sleep AMOUNT;
    $result->set( $_ => \@data );
}
@urls;

{
    no warnings qw(uninitialized);
    my $iter = $result->iterator();
    while ( my ( $url, $data ) = $iter->() ) {
        say $url;
        say for @$data;
        say q(---);
    }
}
__END__
[download]

It works as expected but sometimes i get this confusing error message:

String found where operator expected at /Users/karl/perl5/perlbrew/per
+ls/perl-5.24.1threads/lib/5.24.1/darwin-thread-multi-2level/IO/Socket
+/INET.pm line 303, near "croak 'usage: $sock->peerhost()'"
    (Do you need to predeclare croak?)
# ... many more like this
[download]

This comes from...

sub peerhost {
    @_ == 1 or croak 'usage: $sock->peerhost()';
    my($sock) = @_;
    my $addr = $sock->peeraddr;
    $addr ? inet_ntoa($addr) : undef;
}
[download]

... and many more subs in INET.pm

Update: Replaced $_ with shift. Sorry.

Update2: Mh, it seems when i don't use threads the phenomenon doesn't occur...

Update3: From time to time i get this:

Segmentation fault: 11
Deep recursion on subroutine "IO::Socket::new" at /Users/karl/perl5/pe
+rlbrew/perls/perl-5.24.1threads/lib/5.24.1/IO/Socket/IP.pm line 353, 
+<__ANONIO__> line 2.
[download]

Update4: Switching to WWW::Curl::Easy made it work:

#!/usr/bin/env perl

# The sky may fall on your head tomorrow, but tomorrow never comes
#     $Id: uagent.pl,v 1.5 2017/06/15 13:03:32 karl Exp karl $    

use strict;
use warnings;
use threads;
use MCE::Loop;
use MCE::Shared;
use MCE::Mutex; # who knows what happens ;-)
use WWW::Curl::Easy;
use feature qw(say);
use constant AMOUNT => 0.008;

my $result = MCE::Shared->hash;
my @urls   = qw(http://perlmonks.org http://www.whitehouse.org );

MCE::Loop::init {
    max_workers => 'auto',
    chunk_size  => 1,
    interval    => AMOUNT,
    # posix_exit  => 1, # useless when loading threads
};

my $fetch = sub {
    my $curl = WWW::Curl::Easy->new;
    my ( $header, $body );
    $curl->setopt( CURLOPT_URL,         shift );
    $curl->setopt( CURLOPT_WRITEHEADER, \$header );
    $curl->setopt( CURLOPT_WRITEDATA,   \$body );
    $curl->perform;
    $header;
};

my $mutex = MCE::Mutex->new;

mce_loop {
    MCE->yield;
    my $data = $fetch->($_);
    $data =~ s/\n+$/---/;
    $mutex->enter( $result->set( $_ => $data ) );
}
@urls;

my $iter = $result->iterator();

while ( my ( $url, $data ) = $iter->() ) {
    say qq($url\n$data);
}

__END__

# for i in {1..100}; do ./uagent.pl; done
[download]

Thanks to all fellow monks for help.

Thanks for any hint and best regards, Karl