use strict;
use Data::Dumper;

my ($hash, @array);
my @array = <DATA>;  


$hash ={ map 
			{ chomp; my $key = (split(/\t/) )[0]; 
			$key => [ 
					grep {
							chomp; $_ 
							if( (split(/\t/) )[0] =~/$key/) 
						} @array 
					]  
			} @array 
		};

print Dumper(\%$hash);

__DATA__
1	2	a
1	13	w
1	20	c
2	1	b
2	40	n
3	30	a