Job data is passed to workers by making a shared clone of it. Cloning a shared variable is causing the problem.

Solution that keeps data shared:

use threads;
use threads::shared;

use Data::Dumper         qw( Dumper );
use Thread::Pool::Simple qw( );

my $state :shared = shared_clone({test1 => {test1 => 123}, test2 => {t
+est2 => 'abc'}});

sub worker {
    my ($id) = @_;
    my $data = $state->{$id};
    print "Got Data: ".Dumper($data);
    return { success => 1 };
}

{
    my $tp = Thread::Pool::Simple->new(min => 1, max => 10, do => [ \&
+worker ]);

    my $id1 = $tp->add('test1');
    my $id2 = $tp->add('test2');

    print "return 1: ".Dumper($tp->remove($id1));
    print "return 2: ".Dumper($tp->remove($id2));
}
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Solution that avoids globals:

use threads;
use threads::shared;

use Data::Dumper         qw( Dumper );
use Thread::Pool::Simple qw( );

sub worker {
    my ($data) = @_;
    print "Got Data: ".Dumper($data);
    return { success => 1 };
}

{
    my $state = {test1 => {test1 => 123}, test2 => {test2 => 'abc'}};

    my $tp = Thread::Pool::Simple->new(min => 1, max => 10, do => [ \&
+worker ]);

    my $id1 = $tp->add($state->{'test1'});
    my $id2 = $tp->add($state->{'test2'});

    print "return 1: ".Dumper($tp->remove($id1));
    print "return 2: ".Dumper($tp->remove($id2));
}
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