# The first part is the same as the original.

open IN, $Filename or die "Could not open file $!";
 
@array = ('file', 'this', 'dog', 'forward');
my %guard;
 
READLOOP:
while (<IN>)
  {
   foreach $searchstring (@array)
     {
     if (m/$searchstring/i)
      {
       if (! exists $guard{$searchstring}) {
          push @stringsfound, $searchstring;
          last READLOOP if @stringsfound == @array;
          $guard{$searchstring} = 1;
       }
      }
    }
  }
 
close IN;

# a somewhat nicer output
print join(" ",@stringsfound),"\n";