Looks like homework, but you have done some work and asked for suggestions.

  1. Don't push when you can print.
  2. Usually better to make sub work on one number rather than an array of numbers.
  3. Always use strict and use warnings.
  4. You don't have to predeclare the sub -> Ok to put the loop on the input first.
  5. If I have a good name for the sub, I may not have to be too interested in how it works. With this ordering, I see right away what the program is supposed to do.
My version: 
use strict;
use warnings;

my @input = ( -222, -221, -21, 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89
+, 144 );

foreach my $int (@input)
{
   print "$int " if isSumDigitsOdd($int);
}
print "\n";

sub isSumDigitsOdd
{
    my $num = shift;
    my $sum;
    $sum += $_ foreach (split //, abs $num);
    return ( $sum % 2 );  # return ( $sum & 1 ); would be fine also
}

#prints: -221 -21 1 1 3 5 21 34 89 144

[download]
Update: 1) The name "isSumDigitsOdd" was chosen for a reason. The "is" prefix is one convention for indicating that this returns a flag/boolean value (yes/no). I expect 1 true, 0 false, but tolerate any one bits as true and only all zeroes as false.
2) The foreach loop was also done for a reason..I was able to work in the idea that this expects ints by using $int as the iterator value.
All sorts of details wind up making a difference.

Also:
As an example, I have used the absolute value function abs but I could have used abs($_). Which is best? Does it matter?

I would write abs($_) or even abs $_ rather than just "abs" just to make things more clear even though the generated code is the same. Often there is some descriptive name other than just $_ and I use $_ for simple one line loops like above. Naming loop iterator variables is cheap and improves readability - do it often!

In reply to Re: Newbie question by Marshall
in thread Newbie question by oldB51

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