my %hash;          # crappy name but easy to remember
while (<FILE>)     # assuming FILE is open to the right place
{
    my ($key, $value) = split /\t/;   # only one tab per line
    push @{$hash{$key}}, $value;      # magic of autovivification
}
# done, print everything
foreach my $key (keys %hash)
{
    print $key, " => ", join(' ', values @{$hash{$key}}, "\n";
}