use List::MoreUtils qw( uniq ); sub Remove_duplicate_lines { my ($processed_file, $out_file) = @_; open (PROCESSED_FILE, "<$processed_file"); chomp( my @array = ); close PROCESSED_FILE; my @unique = uniq @array; open (OUTFILE, "+>$out_file"); print OUTFILE join( '', @array ); close OUTFILE; }