remove duplicate words from a line

Perl's robust way of doing the same thing with much simplicity than awk to understand, which we did using awk some time back that removes the duplicate words of every line on per line basis.But,the same word can occur for once in every line.

input : cat a.txt

i am fine sriram
krishna how r u , how r u sriram , How r u jadu
thank you , Thankyou sir, thank you
how r u krishna ? how r u sriram?

required output:

i am fine sriram
krishna how r u , sriram How jadu
thank you , Thankyou sir,
how r u krishna ? sriram?


Script usage: ./merge.pl -file=a.txt

#!/usr/bin/perl -ws
#objective of this script is to remove duplicate words that occur in every line of a file on per line basis, same words can occur for once in every line

our ($file); # switch variable to take file name from command line
my @words; # array of words
my %seen=(); # initalizing a hash

if( !defined $file )
{
      print "Usage: $0 -file=<filename>\n";
      exit 255;

}

unless(open(FH1,"$file")) # check the file , if it doesnot exist throw error
{
      print "couldnot open file: $!\n";
}


if ( -r "$file" )  #if file is readable

{

      while (< FH1 >)
      {
              chomp;
              my @words = split();

              foreach (@words)
              {
                      unless( $seen{$_} ) # every word if it's not seen then increment it in hash value and assign it as hash key
                      {

                              $seen{$_}++ ;
                              push @nodup, $_; # push all words to an  array , $_ is default variable that holds anything
                      }

              }
              push @nodup,"\n"; # after a line,put "\n" at the end before going to next line
              %seen = (); # reinitialize hash before going to next line and traversing every word
      }


}


close(FH1); # close the file at the end
print "@nodup\n"; # print the modifed text at the end