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

my $dir1 = 'Z:\My Documents\Workspace';   #you need single quote here 
my $versionFile = "$dir1\\version.txt";

print "$versionFile\n";   #Z:\My Documents\Workspace\version.txt

my $dirA = "Z:/My Documents/Workspace";   #with / "" is no problem
my $versionFileA = "$dirA/version.txt"; 

print "$versionFileA\n";   #Z:/My Documents/Workspace/version.txt

##</code><code>##

C:\>cd do*
C:\Documents and Settings>