You don't need to define the number of elements, just create the array (empty or with the elements you want) and/or push items into it until you are done.

my $file1 = "foo.txt";
my $file2 = "bar.txt";

my @array1 = ($file1, $file2);

# or

my @array2;
print "Enter a file: ";
while (<>) {
  chomp;
  push @array2, $_;
  print "Enter a file: ";
}
[download]

Does that help?