use strict;
use warnings; 
use File::Glob qw{bsd_glob};

my $string;
my $entry;
do {
  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):  "; 
    my $filename = <STDIN>; 
    chomp $filename;
    open my $fh, "<", $filename or die "Cannot open $filename.\n";
    my $DNA;
    {
      local $/=undef;
      $DNA = <$fh>;
    }
    close $fh;
   
    chomp $DNA;
    $DNA=~s/\n/,/g;
    $string .= "{$DNA}";
  }      # Curly brace for entry1 ends:  
} until ($entry==2);
for (bsd_glob $string) {
  print "~$_~\n";
}