Not forget the immediate import statement if calling require, necessary for the MCE Models.

use strict;
use warnings;
use feature 'say';

require MCE::Map;
import MCE::Map;

MCE::Map-> init(
    chunk_size => 1, 
    max_workers => 4,
    user_begin => sub {
        print "## ", MCE-> wid, " started\n";
    },
    user_end => sub {
        print "## ", MCE-> wid, " completed\n";
    },
);

my @a = MCE::Map-> run( sub { $_ }, [ 0 .. 9 ]);
MCE::Map-> finish;
print "\n", "@a", "\n";

say $MCE::VERSION;

__END__
## 1 started
## 3 started
## 2 started
## 4 started
## 2 completed
## 4 completed
## 1 completed
## 3 completed

0 1 2 3 4 5 6 7 8 9
1.901
[download]

Here is the MCE variant. Ordered output is possible using MCE::Candy.
Note $chunk_id as the first argument to gather. MCE->chunk_id works too.

use strict;
use warnings;
use feature 'say';

require MCE;
require MCE::Candy;

my @in = ( 0 .. 9 );
my @out;

my $mce = MCE-> new(
    chunk_size => 1,
    max_workers => 4,
    user_begin => sub {
        print "## ", MCE-> wid, " started\n";
    },
    user_end => sub {
        print "## ", MCE-> wid, " completed\n";
    },
    user_func => sub {
        my ( $mce, $chunk_ref, $chunk_id ) = @_;
        MCE-> gather( $chunk_id, $_ )
    },
    input_data => \@in,
    gather => MCE::Candy::out_iter_array(\@out),
);

$mce-> run;
$mce-> shutdown;
say "@out";

__END__
## 1 started
## 2 started
## 4 started
## 3 started
## 3 completed
## 4 completed
## 2 completed
## 1 completed
0 1 2 3 4 5 6 7 8 9
[download]