I've had good results with the command line interface to VSS, ss.exe, by shelling out from Perl. I've automated things like checking out files and running Perl scripts against them then checking them back in. The available command line options are documented in the help files.

Edit: Your link to the previous node seems to be broken.

Edit: Here are some examples:

sub checkout_sse_file {
    my ($checkout_path, $filename) = @_;

    if($checkout_path !~ /[\/\\]$/) {
        $checkout_path .= '\\';
    }

    my $sspath= 'C:\Program Files (x86)\Microsoft Visual Studio\VSS\wi
+n32';

    $ENV{SSDIR}="\\\\servername\\dms-sourcesafe";

    my $cmd = "\"$sspath\\ss.exe\" Checkout \"\$/DMS MW/SCADA/Substati
+on Editor Files/$filename\" -C- -I- -GL\"$checkout_path \"";
    #print "\n********************\n\$cmd=$cmd\n";
    # if the file is already there it doesn't download it again. 
    # BUT, it won't overwrite a file unless the read-only bit is set.

    system $cmd;
    return $? >> 8;
}

sub checkin_sse_file {
    my ($checkout_path, $filename, $comment) = @_;

    if($checkout_path !~ /[\/\\]$/) {
        $checkout_path .= '\\';
    }

    my $sspath= 'C:\Program Files (x86)\Microsoft Visual Studio\VSS\wi
+n32';

    $ENV{SSDIR}="\\\\servername\\dms-sourcesafe";

    my $cmd = "\"$sspath\\ss.exe\" Checkin \"\$/DMS MW/SCADA/Substatio
+n Editor Files/$filename\" -C\"$comment\" -I- -GL\"$checkout_path \""
+;
 
    system $cmd;
    return $? >> 8;
}
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