G'day xajin25,

Welcome to the monastery.

You declare and initialise:

my $row = 0;
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You then increment $rowRef which is neither declared nor initialised. Did you mean: ++$row? use strict; would have picked that up; I also recommend you add use warnings; (see strict and warnings). I don't think that's causing your error, though.

You also have "my $keyRef = \$key;" but you don't subsequently make any use of $keyRef. What was your intent with this piece of code?

Your code is incomplete and I don't know what you haven't included; however, I would draw your attention to this from perlthrtut - Shared And Unshared Data:

    In the case of a shared array, all the array's elements are shared, and
    for a shared hash, all the keys and values are shared. This places
    restrictions on what may be assigned to shared array and hash elements:
    only simple values or references to shared variables are allowed - this
    is so that a private variable can't accidentally become shared. A bad
    assignment will cause the thread to die.

Update: This was a poor guess and has been stricken:

$host_info_REF->{$row}->{$key} = $tmp->{$key};
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$host_info{$row}{$key} = $tmp->{$key};
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Here's the type of behaviour I think you're probably after:

#!/usr/bin/env perl

use strict;
use warnings;
use threads::shared;
use Data::Dumper;

my @db_data = (
    { hostname => 'h0', hinfo0 => 'A', hinfo1 => 'B', hinfo2 => 'C' },
    { hostname => 'h1', hinfo0 => 'X', hinfo1 => 'Y', hinfo2 => 'Z' },
);

my %host_info : shared;

my $row = 0;

for my $db_data (@db_data) {
    $host_info{$row} = shared_clone({
        hostname => delete $db_data->{hostname}, host_info => $db_data
    }); 
    ++$row;
}

print Dumper \%host_info;
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Output:

$ pm_thr_compdat.pl
$VAR1 = {
          '1' => {
                   'hostname' => 'h1',
                   'host_info' => {
                                    'hinfo0' => 'X',
                                    'hinfo1' => 'Y',
                                    'hinfo2' => 'Z'
                                  }
                 },
          '0' => {
                   'hostname' => 'h0',
                   'host_info' => {
                                    'hinfo0' => 'A',
                                    'hinfo1' => 'B',
                                    'hinfo2' => 'C'
                                  }
                 }
        };
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You might also find useful information in threads and threads::shared.