#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

my %hash;
while (<>) { # read files from command line (separate by space) e.g. in.txt sample.txt etc...
    next if /^(\s*(#.*)?)?$/; # skip blank lines and comments
    chomp; # lines that are not skipped remove new line character '\n'
    my @tmp = split /:/; # split line on column ':'
    if (exists $hash{$tmp[0]}) { # check if key exists in hash
	$hash{$tmp[0]} .= ":".$tmp[2]; # if exists append
    }
    else {
	$hash{$tmp[0]} = $tmp[2]; # if not exists create new element with data
    }
} continue {
    close ARGV if eof;
}

print Dumper \%hash;

open(my $fh, '>', 'out.txt') # open file to print data
    or die "Could not open file 'out.txt' $!";

while( my( $key, $value ) = each %hash ){ # iterate over the hash
    print $fh $key.':'.$value . "\n"; # write data to file
}

close $fh # close file after finishing
    or warn "Could not close file 'out.txt' $!";

__END__

$ perl test.pl in.txt
$VAR1 = {
          'Thailand' => '6',
          'China' => '2:2:70',
          'Japan' => '6:10'
        };

$ cat out.txt
Thailand:6
China:2:2:70
Japan:6:10