my $dir = 'input_files';

opendir(DIR, $dir) or die "can't opendir $!";
while (defined(my $file = readdir(DIR))) {     # do something with "$dirname/$file" 
  print "The directory and file are $dir/$file\n";
  open (IN, "< $dir/$file"  ) or die ("Can't open input file $!");

  while ( < IN > ){
    print ;
  }
}
closedir(DIR);