But perhaps you are thinking of an array containing empty elements: @array_with_empties = ('ONE', 'TWO', '', 'FOUR');

$array_with_empties[2]) is empty, but exists($array_with_empties[2]); will return a TRUE value! Indeed the array element exists, but is empty.

To check if this array-element is empty, simply test it against the empty element '' or against undef.

And to answer your question: you will always need a loop (explicit or implicit) to check for such elements.

To check if this array-element is empty, simply test it against the empty element '' or against undef.

Empty, a blank string, and undef are different things though!

Update: string, not strong.

They are indeed and zero will also have to be considered in such test, but failing more info of the practical side of what the OP wants, one cannot give more detailed help.

CountZero

A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

Since @userArray2 is empty, it doesn't add anything to @mainArray

my @userArray = qw(batman robin joker);
my @userArray2; #this is a null array

my @mainArray = (@userArray, @userArray2);
print("Number of elements: ", scalar(@mainArray), "\n");   # 3
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If you want to filter out elements of an array, grep is usually the way to go.

my @mainArray = ('batman', 'robin', undef, 'joker');
print("Number of elements: ", scalar(@mainArray), "\n");   # 4
@mainArray = grep { defined } @mainArray;
print("Number of elements: ", scalar(@mainArray), "\n");   # 3
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By the way, adding Array to your variable names is redundant. That's what @ means.

my @userArray = qw(batman robin joker);
my @userArray2; #this is a null array
my @mainArray = (@userArray, @userArray2);
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#@set should consist "batman robin joker", but not
#"batman robin joker NULL"
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my @set = map { exists($_)? $_ : delete($_) } @mainArray;
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-David

my @main = ( @user1, @user2 );
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One thing to consider when looking for that defect is your use of delete on an array element. Doing so will create undefined elements in the list, not remove them.

$array = join /$splitter/, @array; # where $splitter is a scalar that 
+will not be in an element
$array =~ s/$splitter{2,}/$splitter/g;
@array = join $splitter, $array;
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Variations would be required for multi-line strings, of course.

Update: inserted a missing $.

As mentioned, an empty array is not the same as an undefined array, and "0" is defined, so you don't want to skip it.

#!/usr/bin/perl
my (@ar1, @ar2);

$ar1[0] = 1;
$ar1[1] = 0; # a defined element, not NULL
$ar1[7] = 9; # skip, leaving 2..6 undefined

# dump array 1
print("\@ar1:\n");
for my $i (0..$#ar1) {
   print("   $i : $ar1[$i]\n");
}

# weed the undefined elements
@ar2 = grep { defined $_ } @ar1;

print("\@ar2:\n");
for my $i (0..$#ar2) {
   print("   $i : $ar2[$i]\n");
}
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@arr = grep(!/^$/, @arr);

#!/usr/local/bin/perl5.9.5
#
use feature ":5.10";
use strict;
use warnings;


print "content-type: text/html\n\n";

my @userArray = qw(batman robin joker);
my @userArray2; #this is a null array

my @mainArray = (@userArray, @userArray2);

my @set;

# A loop, just for this example...
for(@mainArray)
{
    when ( ! defined $_ ) { next }
    when ( /^$/ ) { next }
    default { push @set, $_ }
}

say "@set";
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