I use an in-memory file, but a real file will do just as well.

{  my $f;
   {  open(my $fh, '>', \$f) or die $!;
      print $fh "abc";
   }
   {  open(my $fh, '<', \$f) or die $!;
      chop( $_ = <$fh> );
      print chop while $_;   # ba
      print"\n";
   }
}

{  my $f;
   {  open(my $fh, '>', \$f) or die $!;
      print $fh "012\n";
   }
   {  open(my $fh, '<', \$f) or die $!;
      chop( $_ = <$fh> );
      print chop while $_;   # 21
      print"\n";
   }
}
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