Oh! Silly me. You call:

main('90   35  29 + 90  24 29')
[download]

But main is:

sub main {
    reduce(@ARGV);
}
[download]

so reduce doesn't see the parameters passed to main, it sees @ARGV which is empty. Change main to:

sub main {
    reduce(@_);
}
[download]

Also:

1. Whatever is natural for the sub. Because of its recursive implementation returning anything except a list from reduce doesn't make sense.
2. There are two different test modes: Functional testing where you test the whole system works as a whole - call main, and unit testing where you test individual units work as advertised - call reduce.

In this case "the whole" is a trivial wrapper around reduce so I'd go for testing reduce directly - a unit test.

You last reply was very helpful! Running the test code manually, my debug print statements in the *.pl file show that the @answer array continues to contain the values from previous calls:

• Test 1. @answer array returns 180 59 58 (test passes).
• Test 2. @answer array returns 179 1 9 180 59 58 (test fails).
• Test 3. @answer array returns 180 0 0 179 1 9 180 59 58 (test fails).
I tried adding

my @answer = undef;
[download]

to the test file main sub definition (thinking that this would get cleared on every call) but that did not work. What do you suggest now?

my @answer = undef;

General note: I'm not sure what you intend by the quoted statement, but you should realize that it initializes the (newly created) array with a single element, the undef value, which in Perl is a well-defined value! (The  @answer array thus created is also entirely and absolutely independent of any other array with the same name.)

c:\@Work\Perl\monks>perl -wMstrict -le
"use Data::Dump qw(dd);
 ;;
 my @answer = undef;
 dd \@answer;
"
[undef]
[download]

---

Give a man a fish:  <%-{-{-{-<