If you don't provide $ARGV[1] (i.e 'remove') on the command line then the code would not enforce removal of any duplicate files...I've changed a little bit in the design of the code to make it easier for me when reading from a fileMD5.txt instead of having to provide for it through $ARGV[0]..

I could not see the reason why a data structure like "$seen{"$md5:$filesize"}" should be used so instead I made the hash key be the filename only, considering that a duplicate file is identified by its name...

The test text file 'fileMD5.txt' contains the following data:

8e773d2546655b84dd  304048    pics/20041004kidscamera/im001020.jpg  im
+001020.jpg
e01d4d804d454dd1fb  296663    pics/20041004kidscamera/im001021.jpg  im
+001021.jpg
8e773d2546655b84dd  304048    pics/20041004kidscamera/im001020.jpg  im
+001020.jpg
8e773d2546655b84dd  304048    pics/20041004kidscamera/im001020.jpg  im
+001020.jpg
8e773d2546655b84dd  304048    pics/20041004kidscamera/im001020.jpg  im
+001020.jpg
8e773d2546655b84dd  304048    pics/20041004kidscamera/im001020.jpg  im
+001020.jpg
e01d4d804d454dd1fb  296663    pics/20041004kidscamera/im001021.jpg  im
+001021.jpg
e01d4d804d454dd1fb  296663    pics/20041004kidscamera/im001021.jpg  im
+001021.jpg
8e773d2546655b84dd  304048    pics/20041004kidscamera/im001020.jpg  im
+001020.jpg
8e773d2546655b84dd  304048    pics/20041004kidscamera/im001020.jpg  im
+001020.jpg
e01d4d804d454dd1fb  296663    pics/20041004kidscamera/im001021.jpg  im
+001021.jpg
e01d4d804d454dd1fb  296663    pics/20041004kidscamera/im001021.jpg  im
+001021.jpg
[download]

Here is just an illustration of a concept that you can incorporate, it gives you a list of unique files on the STDOUT console and a list of those duplicates would be printed onto a temp file, my approach is open for criticism, modification and comments for I am a learner myself, best of luck:

use strict;
use warnings;


my $fileCNT = 0;
my $dupCNT =  0;
my $origCNT = 0;
my %seen;
my %duplicates;


open IN,"< fileMD5.txt" or die ".. we don't see a file to read\n";
print " ... starting to read find duplicats in fileMD5.txt.....\n\n\n"
+;


while(<IN>){
  my $line = $_;
  chomp $line;
  $fileCNT++;
  my ($md5,$filesize,$pathfile,$file) = split /\s+/,$line;
  if(exists $seen{"$file"}){
     $dupCNT++;
     push @{$duplicates{"$file"}}, ([$pathfile,$filesize]);
  }else{
     push @{$seen{"$file"}}, ([$md5,$pathfile,$filesize]);
     $origCNT++;
  }
}


open (TEMP, '>>', "_Duplicate.temp") or die("can not create temporary 
+file\n");
print TEMP "FilePath",' ' x 40,"File Size\n\n";
for my $key(keys %duplicates){
    my $lineNo=1;
    for my $info(@{$duplicates{$key}}){
        print TEMP "@{[$lineNo++]}:@$info\n\n\n";
        }
   }
print "\U\t\toriginal files:\E\n\n";
print "FileName",' 'x20,"Location",' 'x 20,"size\n";
print "_" x 70,"\n";
for my $key(keys %seen){
    my $lineNo = 1;
    for my $info(@{$seen{$key}}){
        print "@$info\n";
        }
    }
   
print "\n\n\USummary\E:files: $fileCNT  originals: $origCNT  files dup
+licated: $dupCNT.\E\n\n";
#use Data::Dumper;
#print Dumper(\%duplicates);
#print Dumper(\%seen);
[download]

Output to console:

 ... starting to read find duplicats in fileMD5.txt.....


        ORIGINAL FILES:

FileName                    Location                    size
____________________________________________________________________
8e773d2546655b84dd pics/20041004kidscamera/im001020.jpg 304048
e01d4d804d454dd1fb pics/20041004kidscamera/im001021.jpg 296663


SUMMARY:files: 12  originals: 2  files duplicated: 10.
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Output to temp file:

FilePath                               File Size

1:pics/20041004kidscamera/im001020.jpg 304048


2:pics/20041004kidscamera/im001020.jpg 304048


3:pics/20041004kidscamera/im001020.jpg 304048


4:pics/20041004kidscamera/im001020.jpg 304048


5:pics/20041004kidscamera/im001020.jpg 304048


6:pics/20041004kidscamera/im001020.jpg 304048


1:pics/20041004kidscamera/im001021.jpg 296663


2:pics/20041004kidscamera/im001021.jpg 296663


3:pics/20041004kidscamera/im001021.jpg 296663


4:pics/20041004kidscamera/im001021.jpg 296663
[download]