$/ = undef;
my $string = <IN>;

my @all = split /\t|\n/,$string;
my @array;

for ($i=0; $i<$#all; $i+=2)

{	$array[$all[$i]] [$all[$i+1]] = 1 ; 
	$array[$all[$i+1]] [$all[$i]] = 1 ;
}