Persistent issue installing the `fuzzy-logic-toolkit-0.4.5`

My system is Linux Ubuntu 20.04, GNU Octave, version 5.2.0

I've tried this multiple times, in multiple ways, but the result is always
the same: 

```
>> pkg list
no packages installed.
>> pkg install -forge fuzzy-logic-toolkit
parse error near line 165 of file
/home/seamus/octave/fuzzy-logic-toolkit-0.4.5/defuzz.m

  anonymous function bodies must be single expressions

>>>   y_val = @(y_val) if (y_val == max_y) 1 else 0 endif;
                        ^

error: called from
    doc_cache_create>create_cache at line 109 column 20
    gen_doc_cache_in_dir>@<anonymous> at line 143 column 16
    doc_cache_create>gen_doc_cache_in_dir at line 144 column 9
    doc_cache_create at line 55 column 12
    install>generate_lookfor_cache at line 802 column 5
    install at line 231 column 7
    pkg at line 441 column 9
>>
``` 

What is wrong, please? Any fixes on the horizon? Any suggestions on how to
resolve this so I can get on with my business? FWIW, never used Octave until
today. I installed it specifically to evaluate the fuzzy logic module... off
to a bad start :(  




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