So, what I think is being said is that the script this is in needs an OS checker so it can load a Win32 specific utility to do the job?

I have a df utility on my windows system -- part of the UnxUtils package though it segfaults on my 64-bit OS -- but generally most windows systems will not have it, and expecting users to find and install one is naive.

Far simpler I think to use something like:

sub freespace {
    if( $^O eq 'MSWin32' ) {
        `fsutil volume diskfree .` =~ m[avail free bytes  : (\d+)]; 
        return ( $1 // die $! ) / 1024;
    }
    elsif( $^O eq ... ) {
        ...
    }
    else {
        `df -k .` =~ m[...]; 
        return $1 // die $!
    }
}
...

my $free = freespace();
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