That was it! Mixing SSH2 and SFTP commands is a bad thing. For the sake of future Novices, I'm posting change required to get the sample script working:

Replace the original code block (around line 157):

    printf("# scp_get(%s,%s)\n", $myFile, $localDir . "\\$myFile");

    $rc=$ssh2->scp_get($myFile, $localDir . "\\$myFile");
    printf("# rc=%s\n", defined($rc)?$rc:"<UNDEFINED>");
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# vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
        # The previous code block was replaced with code to
        # open remote and local files, then read the remote file
        # and write it to the local file.
        # The binmode() call is necessary because this is a
        # Windows(tm)-to-UNIX transfer and line-endings must
        # be preserved.
        my $rfh;    # Remote File Handle
        $rfh = $sftp->open($sftpRemoteDir . "/" . $myFile);
        if (defined($rfh))
        {
            if (open(LFH, ">$localDir\\$myFile"))
            {
                my $myLine;    

                    # Force binary transfers to preserve line endings
                    # when transferring between Windows and UNIX.
                binmode(LFH);

                while ($myLine = <$rfh>) 
                {
                    printf(LFH "%s", $myLine);
                }
                close(LFH);
            }
            else
            {
                # ERROR: Could not open local file for transfer
                printf("Could not open local file '%s' for transfer\n"
+,
                            $myFile);
            }
        }
        else
        {
            # ERROR: Could not open remote file for transfer
            printf("Could not open remote file '%s' for transfer\n",
                            $myFile);
        }
[download]

Many thanks for your help! You saved me hours of banging my head against a wall!

Kevin