use strict;
use warnings;
my %hash = map {
     (split /:/, $_ )[0] => (split /:/, $_ )[2]
    } <DATA>;
print join ( "\n", sort keys %hash ) . "\n";
__DATA__
k1:asd:v1
k2:asd:v2

##</code><code>##

  map {
    my @tmp = split /:/, $_;
    $tmp[0] => $tmp[2];
  } <FILE>