Hi Perl Monks,

There is a real-world application for this, but I'm going to make it simple for the sake of the example.

Let's say I have an array of characters:

 my @chars = qw( a b c ? : ! f g )

And I have a function called "getUpperCaseChars" that converts those characters to their uppercase equivalents. But for the punctuation, since it has no uppercase equivalent, it returns an undef for those indices instead: 

my @upChars = getUpperCaseChars( @chars );
# @upChars is now ( 'A', 'B', 'C', undef, undef, undef, 'F', 'G' )

[download]

Now after I've called getUpperCaseChars(), I can determine which ones did not have uppercase equivalents by doing something like this: 

my @charsWithNoUpperCase =
    @chars[grep { !defined @upChars[$_] } 0..$#upChars];

[download]

But readability is low on that, so I've changed it to a foreach: 

my @charsWithNoUpperCase
foreach my $index ( 0..$#upChars ) { 
    push @charsWithNoUpperCase, $chars[$index]
        if !defined $upChars[$index];
}

[download]

So my question is, is using the array slice significantly more efficient?

In reply to Array slice vs foreach and push by chrisburel

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