SelectSaver - save and restore selected file handle

SYNOPSIS

           use SelectSaver;

           {
              my $saver = new SelectSaver(FILEHANDLE);
              # FILEHANDLE is selected
           }
           # previous handle is selected

           {
              my $saver = new SelectSaver;
              # new handle may be selected, or not
           }
           # previous handle is selected

DESCRIPTION

       A SelectSaver object contains a reference to the file
       handle that was selected when it was created.  If its new
       method gets an extra parameter, then that parameter is
       selected; otherwise, the selected file handle remains
       unchanged.

       When a SelectSaver is destroyed, it re-selects the file
       handle that was selected when it was created.