#!/usr/bin/perl -w
use strict;

use MCE;
use DBD::Oracle;
use DBI;

sub myBegin {
    my ($mce) = @_;
    $mce->{db} = DBI->connect(
       "dbi:Oracle:<SERVER_NAME>", "<USERID>", "<PASSWORD>"
    ) || die($DBI::errstr . "\n");
    return;
}

sub myEnd {
    my ($mce) = @_;
    $mce->{db}->disconnect;
    return;
}

sub mySub {
    my ($mce, $chunk_ref, $chunk_id) = @_;
    my $db = $mce->{db};

    return;
}

my (@array, $mceObj, $db);

$db = DBI->connect(
   "dbi:Oracle:<SERVER_NAME>", "<USERID>", "<PASSWORD>"
) || die($DBI::errstr . "\n");

...do some work with the database in order to fill up
...the @array variable...

$db->disconnect;

$mceObj = MCE->new(max_workers => 4,
                   input_data => \@array,
                   user_begin => \&myBegin,
                   user_func => \&mySub,
                   user_end => \&myEnd);

$mceObj->run;