You could use a hashref (which you're nearly doing):

sub foo {
    #...
    return { errno => 0, errmess => $msg };
}

my $error = foo();
print $error->{errno}, $error->{errmess};
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Or, you can use lists:

sub foo {
    #...
    return ( 0, $msg );
}

my ( $errno, $errmess ) = foo();
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Also, watch out for:

if ($var = 0) {
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That's going to assign zero to $var. If you start all your scripts with:

use strict;
use warnings;
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perl will catch that for you (as well as many other errors & warnings).

update: used parentheses instead of braces. doh.