#!/usr/bin/perl
use strict;
use warnings;

if (!-d "sorted")
{
    mkdir "sorted" or die "unable to create dir sorted $!";
}

my @files2sort = <file*.txt>;  #just use glob to get names
my $curfilenum =1;

foreach my $file (@files2sort)
{
   open my $fh_in, '<', $file  or die "$file failed to open $!";
   open(my $fh_out, '>', "./sorted/$file.sort") or die "cannot create out $file.sort $!";
   
   print "Processing ".$curfilenum++." of ".@files2sort." $file\n";
   sortfile($fh_in, $fh_out);

   close ($fh_out);
   close ($fh_in);
   print "OK: Sorted $file \n";
}

sub sortfile 
{
   my ($fh_in, $fh_out) = @_;
   
   my @lines = <$fh_in>;
   
   my @sorted = map { $_->[0] }
                sort { $a->[1] <=> $b->[1] }
                map { my ($x) = $_ =~ /VerNumber:\((\d+)/i; [$_, $x]; }
                @lines;
      
   print $fh_out @sorted;
}    


__END__
Processing 1 of 2 file1.txt
OK: Sorted file1.txt 
Processing 2 of 2 file2.txt
OK: Sorted file2.txt 

#these names are confusing...
my $files_size = $#files + 1;
my $index_file = 1;

#better names?:
my $num_files = @files; 
# the value of an array in a scalar context is the
# number of items in the array, no need for $#files+1
# or you can just use @files in a scalar context without
# creatng $num_files at all. 

my $file_counter =1;
#  "$index_file" would mean something different