my %HoA;

while (<>)
{
    chomp;
    my( $category, $item ) = split /\t/, $_, 2;
    push @{$HoA{$category}}, $item;
}

for my category ( sort keys %HoA )
{
    local $" = ", ";
    print "$category: @{$HoA{$category}}\n";
}