I've Googled and tried a lot last week, but I'm stuck (on the syntaxis).

I hope you understand my message despite the wording

Actually it seems more like you're stuck on syntax and arrays.

You need to read perlintro and Basic debugging checklist and How do I post a question effectively? and References quick reference

Also, when you have a program, with real, named variables, talking about columns can get confusing , talk about your variables instead ;)

The code you pasted will never have a 12 element array, nor do you want one.

I would go back to

my @sorted =
   map substr($_, 8),
   sort
   map join('', (/(..)-(..)-(....)/)[2,1,0], $_),
   @dates;  # DD-MM-YYYY
[download]

Don't get it? To understand, you would write a program like this

#!/usr/bin/perl --
use strict;
use warnings;
use Data::Dumper;
my @dates = qw[
    08-15-2011
    08-10-2011
    08-05-2011
];

print "\ndates ", Dumper( \@dates );

#~ my @firstTransform =  map join('', (/(..)-(..)-(....)/)[2,1,0], $_)
+, @dates;  # DD-MM-YYYY
my @firstTransform =  map join('', ReorderForCmp($_), $_), @dates;  # 
+DD-MM-YYYY
print "\nfirstTransform ", Dumper( \@firstTransform  );

my @firstSorted = sort @firstTransform  ;
print "\nfirsSorted ", Dumper( \@firstSorted  );

my @finalTransform = map substr($_, 8), @firstSorted ;
print "\nfinalTransform ", Dumper( \@finalTransform );

sub ReorderForCmp {
    my( $one ) = @_;
    my @date = $one =~ /(..)-(..)-(....)/;

#~     return @date[2,1,0];
    return $date[2], $date[1], $date[0];
}

__END__
[download]

which produces this output

dates $VAR1 = [
          '08-15-2011',
          '08-10-2011',
          '08-05-2011'
        ];

firstTransform $VAR1 = [
          '2011150808-15-2011',
          '2011100808-10-2011',
          '2011050808-05-2011'
        ];

firsSorted $VAR1 = [
          '2011050808-05-2011',
          '2011100808-10-2011',
          '2011150808-15-2011'
        ];

finalTransform $VAR1 = [
          '08-05-2011',
          '08-10-2011',
          '08-15-2011'
        ];
[download]

So yes, it is possible to "map two columns date and time", just adjust sub ReorderForCmp to return iso-8601 style datetime ( YYYYMMDDHHMMSS)

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