use v5.14;

my $dir = "C:\\Users\\Desktop\\collection2";

opendir(DR, $dir) || die "could not open directory: $!\n";
my @docs = grep{/[^\.|..]/} readdir DR;
closedir DR;

while ( chomp(my $query = <>) ) {   
   foreach my $doc (@docs){
      open(DOC,'<',"$dir\\$doc") or die "$!\n";
      while(<DOC>){
         chomp;
         if($query =~ m/$_/i){
            print "$query appears in $doc\n";
         }
      }
      close DOC;
   }
}