It looks to me like you don't even need to get the list of files in the directory. Just use -e to check that a file in your list exists in the folder:

     foreach my $file (@strings) {
          next unless -e $file; # ignore this file if it doesn't exist
          # your code here
     }
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NB: when declaring a scalar with my, the undef is implicit, so my $scalar; is enough. But when you write an array my @array; is an empty array, but my @array = undef; is an array with one undefined element ; the size of the array is 1 instead of 0.