use strict;
use warnings;

use Config;
print STDERR qq!Perl $^V on $^O arch $Config{archname}\n!;

sub demo {
  my ($s1, $s2) = ('','');
  my $sFormat = "s1='%s' s2='%s'\n";

  open(my $fh1, '>', \$s1) or die "Can't open fh1";
  print $fh1 'Hi Thing One';
  printf STDERR $sFormat, $s1, $s2;
  # => s1='Hi Thing One' s2=''

  open(my $fhSave, '>&', $fh1) or die "Can't save fh1";
  close $fh1;
  open($fh1, '>', \$s2) or die "Can't redirect fh1";
  print $fh1 'Hi Thing Two*Bye Thing Two';
  printf STDERR $sFormat, $s1, $s2;
  # => s1='Hi Thing One' s2='Hi Thing Two*Bye Thing Two'

  # PICK ONE OF TWO OPEN OPTIONS BELOW
  #1#
  #print STDERR "Option 1\n"; open($fh1, '>&', $fhSave)                     or die "Can't restore fh1";

  #2#
  #print STDERR "Option 2\n";open($fh1, '>', \ substr($s1, length($s1)) )  or die "Can't restore fh1";

  print $fh1 '*Bye Thing One';
  printf STDERR $sFormat, $s1, $s2;

  # OUTPUT FROM OPEN OPTIONS
  #1# => s1='Hi Thing One' s2='Hi Thing Two*Bye Thing Two'
  #2# => s1='Hi Thing One*Bye Thing One' s2='Hi Thing Two*Bye Thing Two'
}
demo();
exit(0);