G'day Michael W,

To my mind, the following is cleaner, more readable, and more maintainable. Here's the basic changes:

• Moved the static data out of the loop: doesn't need to be redefined on every iteration.
• Reused the test data from choroba's 3rd code example.
• Made the elements of the array actual references. You used $Date_Ref which is poorly named because they're strings, not references.
• The loop now just contains two statements: much easier to read and maintain.

#!/usr/bin/env perl

use strict;
use warnings;

my %months;
@months{qw{Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec}}
    = '01' .. '12';
my $out_fmt = '%4d-%s-%02d';

my ($Map_Request_Date,
    $Map_Due_Date,
    $Map_Cutover_Date,
    $Map_Complete_Date,
    $Map_Approved_Date
) = (
    'Jan  1 2017 12:00',
    'Jan 31 2017 12:00',
    'Feb 28 2017 23:59',
    'Mar  1 2017 12:01',
    'Dec 31 1999 0:01'
);

my @var_refs = \(
    $Map_Request_Date,
    $Map_Due_Date,
    $Map_Cutover_Date,
    $Map_Complete_Date,
    $Map_Approved_Date
);

print "$$_\n" for @var_refs;

for (@var_refs) {
    my ($m, $d, $y, undef) = split ' ', $$_;
    $$_ = sprintf $out_fmt, $y, $months{$m}, $d;
}

print "$$_\n" for @var_refs;
[download]

Output:

Jan  1 2017 12:00
Jan 31 2017 12:00
Feb 28 2017 23:59
Mar  1 2017 12:01
Dec 31 1999 0:01
2017-01-01
2017-01-31
2017-02-28
2017-03-01
1999-12-31
[download]

Update: It looks like I mis-clicked on your last post instead of your current post, and replied to that. Hopefully, there's still some useful information. [See "Re^5: Array of variables" for some more details about that.]