You say you are having difficulty, but you don't say what the difficulty is very clearly, making it difficult to help.

Perhaps the following will give you some ideas. Otherwise, you might be a bit more specific about what the difficulty is.

#!C:/strawberry/perl/bin/perl.exe
#
# See http://rick.measham.id.au/pdf-api2/
#
use strict;
use warnings;
use Data::Dumper::Concise;

my @records;

while(my $record = <DATA>) {
    push(@records, [ split(/\s+/, $record) ]);
}

report({
    group_by    => 0,
    sum_columns => [ 2, 3 ],
    records     => \@records,
});

report({
    group_by    => 1,
    sum_columns => [ 2, 3 ],
    records     => \@records,
});

report({
    group_by    => 2,
    sum_columns => [ 3 ],
    records     => \@records,
});

exit(0);


sub report {
    my ($args) = @_;


    # sum columns by group
    my %groups;
    foreach my $record (@{$args->{records}}) {
        my $group = $groups{$record->[$args->{group_by}]} //= {};

        $group->{count}++;

        foreach my $sum_column (@{$args->{sum_columns}}) {
            $group->{sum}->{$sum_column} += $record->[$sum_column];
        }
    }

    # produce output
    print "example output: group by column $args->{group_by}, sum colu
+mns " .
        join(', ', @{$args->{sum_columns}}) . "\n";
    foreach my $group (sort keys %groups) {
        print join(' ',
            $group,
            map {
                (
                    $groups{$group}->{count},
                    $groups{$group}->{sum}->{$_}
                )
            } @{$args->{sum_columns}}
        ) . "\n";;
    }

    print "\n";
}




__DATA__
U1     ID1     100     280
U1     ID1     137     250
U2     ID2     150     375
U1     ID2     100     100
U3     ID1     100     600
U9     ID3     137     200
[download]

Which produces:

example output: group by column 0, sum columns 2, 3
U1 3 337 3 630
U2 1 150 1 375
U3 1 100 1 600
U9 1 137 1 200

example output: group by column 1, sum columns 2, 3
ID1 3 337 3 1130
ID2 2 250 2 475
ID3 1 137 1 200

example output: group by column 2, sum columns 3
100 3 980
137 2 450
150 1 375
[download]