use String::ShellQuote;                        # this package almost never works

my $Temp = shell_quote_best_effort('BulletinV3, 1 Montana 20xx-xx-xx (print).pdf_FN_TEMPLATE');

if (-e $Temp) {
    `zenity --width 300 --info  --text 'DBG> Got it!'`;
    }
  else {
    `zenity --width 300 --error --text 'DBG> Nope, not found!'`; # this is what I get all the time
    }

$rc = rename("BulletinV3, 1 Montana 20xx-xx-xx (print).pdf_FN_TEMPLATE",
             "BulletinV3, 1 Montana $SundayDate (print).pdf_FN_TEMPLATE");
if($rc == 1) {
    $ExtTypes{'pdf_FN_TEMPLATE'}++;
    }
  else {
    `zenity --title \"Rename problem\" --width 400 --error --text \"File rename error (\\\"$!\\\"; \\\"BulletinV3, 1 Montana 20xx-xx-xx (print).pdf_FN_TEMPLATE\\\")\"`;
    }