#!/usr/bin/perl 

#1 add use strict
use strict;
use warnings; 

#2 add ''
use File::Glob('bsd_glob');

#3 declare variables 
my (@array,@DNA,@list);
my ($filename,$combi,$entry,$number,$DNA);
do { 
  #4 not needed @array=@array1;
  print"\n\n Press 1 to Enter New File or 2 to Combine:  ";
  $entry=<STDIN>; 
  chomp $entry;  

  if ($entry==1) { 
    print"\n\n    Enter New File Name (.txt):  "; 
    $filename = <STDIN>; 
    chomp $filename;
    unless ( open(FILE, $filename) ) {
      print "Cannot open file \"$filename\"\n\n";
      exit;
    } 
    @DNA= <FILE>;
    close FILE;
    #5 add chomp
    chomp(@DNA);
    #6 add join by comma
    $DNA = join(',',@DNA);    
    push @array, $DNA;
    #7 not needed @array1=@array;
  } elsif ($entry==2) { 
  
    #8 @array1 not needed use @array
    #@array1=@array; # Curly brace for entry2 starts
    $number=@array; 
    print"\n\n No. of Elements in Joined Array: $number\n";
    print"\n Joined Array:\n";
    print "@array\n";           

    #9 none of this code required because comma added a #6
    # Use of foreach LOOP to view each element of joined array: 
    #num=0; 

    #foreach my $element (@array1) { 
      # $num++;    
      # print"\n  Array No.$num of the Joined Array:\n"; 
      # print $element;
      # print"\n"; 
      # Code to surround each element of joined array
      # followd by comma i.e. [ ],  

	  # @element=split('',$element);  
      # $str1 = sprintf '[%s],'x @element,@element; 
      # print"\n str1: $s\n"; 
	  #push @ARRAY1,$element; 

    #} # Curly brace for foreach ends: 

    #print"\n ARRAY:\n"; 
    #print @ARRAY1; 
	#print"\n"; 

    # To produce all possible combinations of different elements: 
    #10 use simple $_ on @array
	#$combi = join('',map {'{'.join (',',@$_).'}'} @ARRAY1);  
	$combi = join('',map {'{'.$_.'}'} @array);
	print "combi = $combi\n";
    @list = bsd_glob($combi); 
  
    print"\n Results:\n"; 
	#11 print each element on new line
    print join "\n",@list; 

  } # Curly brace for Entry 2 ends: 
} until ($entry==2); # Square bracket for do-until: 
exit;