How to get Octave.app to work?

[Vic Norton]

Macintosh only.

I am trying to get the octave-2.9.13 in Octave.app to run from within  
a perl  script. Before I get into that I am stymied by an error I get  
from octave-2.9.9. Can anyone tell me what is going wrong?

Here's the problem in its simplest form.

Test 1. From terminal I execute
   vic$ /Applications/Octave.app/Contents/Resources/bin/octave
This gets me into octave-2.9.13. Now I execute
   octave-2.9.13> printf("%d\n", fopen ("~/desktop/ 
octave_output.txt", "wt"));
The output is
   3

Test 2. From terminal I execute
   vic$ /usr/local/bin/octave
This gets me into octave-2.9.9. Now I execute
   octave> printf("%d\n", fopen ("~/desktop/octave_output.txt", "wt"));
The output is
   -1

What is going on? Why can octave-2.9.13 see the "octave_output.txt"  
file when octave-2.9.9 cannot. Moreover, there doesn't seem to be  
anything wrong with my octave-2.9.9. I am constantly opening other  
files for writing, in essentially the same way, with octave-2.9.9.

Any advice you can give me on this mystery would be greatly appreciated.

Regards,

Vic