FTR: This code shows that the behaviour of treating the filename '""' as an alias for CWD, is an inherent part of the Windows API:

#include <windows.h>
#include <stdio.h>

int main( int argc, char **argv ) {
    char *file = "\"\"";
    char buf[ 1024 ];

    GetFullPathName( file, 1024, buf, NULL );
    printf( "%s -> %s\n", file,  buf );

    return 1;
}
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Build and run:

C:\test>cl /W3 GetFullPathName.c
Microsoft (R) C/C++ Optimizing Compiler Version 15.00.21022.08 for x64
Copyright (C) Microsoft Corporation.  All rights reserved.

GetFullPathName.c
Microsoft (R) Incremental Linker Version 9.00.21022.08
Copyright (C) Microsoft Corporation.  All rights reserved.

/out:GetFullPathName.exe
GetFullPathName.obj

C:\test>GetFullPathName
"" -> C:\test\""
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And exposed to Perl directly via:

C:\test>perl -MWin32 -E"say Win32::GetFullPathName( '\"\"' )"
C:\test\""
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