purl in your heart: How to make group_by_in

$ typeset -f group_by_in_perl
group_by_in_perl ()
{
perl -F\\t -lane 'BEGIN{$group_by=shift; $sum_by=shift} END { print for map{ join qq(\t), $_, $sum{$_}} keys %sum } $sum{join qq(\t), @F[eval($group_by)]} += $F[eval($sum_by)]' $*
}