So you're saying that you get the specified warning when you try to chdir to Z:/Partners/Wilsons/2push_test?

Can you, from the command line, cd Z:\Partners\Wilsons\2push_test successfully?

These are all Strawberry Perl installs, that I ran this code against:

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

use Cwd;

say getcwd();
chdir 'c:/repos' or die $!;
say getcwd();
[download]

Output:

c:\>berrybrew exec perl chdir.pl

Perl-5.24.0_64
==============
c:/
c:/repos


Perl-5.22.2_64
==============
c:/
c:/repos


Perl-5.18.4_64
==============
c:/
c:/repos


Perl-5.10.1_32
==============
c:/
c:/repos
[download]

So using forward slashes without escaping them most definitely works all the way back to at least 5.10.