#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11123126
use warnings;

my %hash;
my $current;

while( <DATA> )
  {
  if( /(\w+):\n/ )
    {
    $hash{$1} = $current = {};
    }
  elsif( /(\w+):(\w+)/ )
    {
    $current->{$1} = $2;
    }
  }
use Data::Dump 'dd'; dd \%hash;

__DATA__
first:
this:that
here:there
when:what
how:where
now:later
name:onlyfirst

second:
this:that
here:there
when:what
how:where
now:later
name:onlysecond