As poj suggested, in these modern days importing into a relational database like Microsoft Access or sqlite might provide an easy SQL solution to your problem. If you want to look at your files as a text database then the problem looks like it fits an old text database processing tool: Awk. Perl has an awkish/autosplit '-a' mode suggesting:
#!/usr/bin/perl -a
use strict;
use warnings;
our %recs;
my $k = join "\t", @F[0 .. 3];
if ($recs{$k}) {
$recs{$k}->{key_count}++;
$recs{$k}->{rec}->[$_] += $F[$_] for 4, 5;
}
else {
# careful to copy with [ @F ] not \@F here
$recs{$k} = {key_count => 1, rec => [ @F ]};
}
END {
$recs{$_}->{rec}->[4] /= $recs{$_}->{key_count} foreach keys %recs
+;
print join("\t",@{$recs{$_}->{rec}}), $/ foreach sort {
$recs{$a}->{rec}->[ 0 ] cmp $recs{$b}->{rec}->[ 0 ] ||
$recs{$a}->{rec}->[ 1 ] <=> $recs{$b}->{rec}->[ 1 ] ||
$recs{$a}->{rec}->[ 2 ] cmp $recs{$b}->{rec}->[ 2 ] ||
$recs{$a}->{rec}->[ 3 ] cmp $recs{$b}->{rec}->[ 3 ]
} keys %recs;
}
