my @combinedData;
my @currentFile;
my @filesList = <*>;

foreach my $file (@filesList) {
   open(F, "file.txt") or die("Unable to open file");
   @currentFile = <F>;
   # HOW TO COMBINE IT INTO @combinedData ?
   # if I do it thru a reference the content 
   # will change in the next loop when I modify @currentFile
   # again
   ...
}