Win32's GetFullPathName and GetLongPathName will do that.
The former also converts the path to an absolute path.
The latter also expands short file names into long file names.

use Win32 qw( );

# Win32 doesn't export these, so we'll import them manually.
BEGIN {
   no strict 'refs';
   *$_ = \&{"Win32::$_"}
      for qw( GetLongPathName GetFullPathName );
}

my $path = "\\DOCUMENTS AND SETTINGS";

# If you wish to keep relative paths relative:
print GetLongPathName($path); 

# If you wish to make relative paths absolute:
print GetLongPathName(scalar(GetFullPathName($path)));
[download]

Note that Win32's GetCwd returns the path as provided to chdir.

Tested.

I ran into a similar problem recently. I believe the issue mentioned in the original post "but it returns the directory exectly the way it was typed" is referred to by Microsoft as the feature of being "case insensitive but case preserving". By "case preserving" they do not seem to mean that they preserve the case of the file (or directory) to the case that was used when it was created but that they preserve the case as was used when it was accessed; this is a weird feature.

The "use Win32" solution means that one needs to branch the user-script based on the OS. I tried to solve the problem using

use Cwd qw(getcwd chdir realpath);
use File::Spec::Functions;  # canonpath
[download]

but was not successful -- even canonpath(realpath()) respects the "case preserving" "feature".

Using the same path you provided avoids confusion. Unix usually does the same thing. If you use /home/ikegami/symlink/dir, it won't magically become /some/where/else/dir.

File::Spec definitely won't help, since it doesn't do any system calls.

You could always do a directory listing for every component of the path and look for the matching name. That can fail due to permissions and if one of the components is an 8.3 name, but you can always fall back to what you were provided for those components.

Finally, so what if you have to branch. You're asking to do something platform-specific, after all. Just hide it in a module with a thin, portable interface. It can call Win32::GetLongPathName on Windows and File::Spec->canonpath on other platforms.

Windows, right? It helps if you clarify when writing these questions :)

Possibly abs_path can help?

use strict;
use warnings;
use Cwd qw(abs_path);

chdir("C:\WINDOWS\PROGRAM FILES"); # <- or whatever it is in windows.

my $thisdir = abs_path('.');

print "This dir is $this_dir\n";
[download]

Untested (I'm in Linux), but that would be my first stab at this.

Sorry, that doesn't work :( and not just cause your slashes are unescaped ;)
getcwd, cwd and abs_path all return paths using the same caps provided to chdir (and with the slashes reversed to /).