Depending on what you're doing you may want to use a hash instead. If the main thing you're concerned with is whether your collection already contains something you should use a hash instead. Instead of searching the entire array for each an item which takes O(n) time a lookup in a hash takes O(1). This means that if your array size doubles your search time on average will double as well. A hash has a constant lookup time will remain the same whether the hash contains 1 or a million items. For an example we'll read a line from the keyboard and if we've seen it already we'll add it to our "collection".

my %set #how you initialize an array
while($line=<>) #while text is coming in from the keyboard 
                #set $line=line of keyboard input
{
    unless($set{$line}){
      $set{$line}=1;  # basically means we've seen this line
    }
}

#now lets see each $line we've encountered
foreach my $line(keys %set){
   print $line;
}
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Hope this helps you might also want to look at The Basic Datatypes, three for more info on hashes. There is also a similar question in the faq about How can I tell whether a list or array contains a certain element?