In this case, a join is unnecessary (but still perhaps valuable for others that need to do similar acts in the future):

@a = (1, 2, 3);

print @a;
print $a[0], $a[1], $a[2];  # equivalent to @a
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Passing arguments to a function (even internal) as an array is just like passing a list of your own individual arguments. In this case, however, each element will be printed one after another. If you want to separate with spaces, either set $, or use join as you've done.

If you're working from a list generated from a file, though, as we are here, newlines are still at the end of each element in the list, so printing them out like he's doing will have the desired effect:

@list = <INPUT_FILE>;
print OUTPUT_FILE @list;   # exact (textual) copy
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