use strict;
use warnings;

my $file = 'file.txt';
open(my $fh, '<', $file)
   or die("Unable to open input file \"$file\": $!\n");

my %hash;
while (<$fh>) {
   chomp;
   my ($dtype, $rest) = split(/:/,  $_,    2);
   my ($id,    $desc) = split(/\t/, $rest, 2);
   $hash{$id} = $desc;
}

##</code><code>##

while (<$fh>) {
   my ($id, $desc) = /^[^:]*:([^\t]*)\t(.*)$/;
   $hash{$id} = $desc;
}