There is one time when you will want to use a while loop for an array (that I can think of) and that is if you are adding items to the array while iterating through it. for(each) will not reflect changes to the array once the loop has started. A good example of something like this is traversing a directory structure....

#This code not tested

my @dirs = '.';
while(my $dir = shift @dirs) {
  opendir(DIR,$dir);

  while(my $entry = readdir(DIR)) {

    if(-d $entry) {
      push @dirs, "$dir/$entry";
    } else {
      #do something for files/links etc
    }

  }

  closedir(DIR);
}
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Just thought I would point that out. for basically makes an in-memory copy of the list when it first starts.