add simple command line opts

filter.pl

@@ -1,22 +1,50 @@
 #!/usr/bin/perl
 
 use strict; use warnings;
+use Getopt::Long;
+
+my $newlines = '';
+my $file = '';
+GetOptions ("newlines" => \$newlines, # print newlines
+            "file=s" => \$file # input file
+) or die("Error in command line arguments\n");
 
 my %seen = (); 
 
-for (;;) {
-  my $input = <STDIN>;
-  last if not defined $input;
-  chomp $input;
-  my @l = $input =~ /([0-9]+\/[0-9]+\/[0-9]+)/mg;
-  foreach my $item (@l) {
-    $seen{$item}++;
+my $in_file;
+
+if ($file) {
+  open my $in_file, $file or die "Could not open $file: $!";
+  while (my $line = <$in_file>) {
+    last if not defined $line;
+    chomp $line;
+    my @l = $line =~ /([0-9]+\/[0-9]+\/[0-9]+)/mg;
+    foreach my $item (@l) {
+      $seen{$item}++;
+    }
+  }
+  close $in_file;
+} else {
+  for (;;) {
+    my $input = <STDIN>;
+    last if not defined $input;
+    chomp $input;
+    my @l = $input =~ /([0-9]+\/[0-9]+\/[0-9]+)/mg;
+    foreach my $item (@l) {
+      $seen{$item}++;
+    }
   }
 }
 
 my @uniq = sort gw_comp keys %seen;
 if (@uniq) {
-  print "@uniq\n";
+  if ($newlines) {
+    foreach my $item (@uniq) {
+      print "$item\n";
+    }
+  } else {
+    print "@uniq\n";
+  }
 }
 
 sub gw_comp{