my @AoA;
foreach (@transactions) { #there are dozens of employee numbers…
        push @{$AoA[$_]}, $_;
}

##</code><code>##

my %HoA;
foreach (@transactions) {
        my ($name, $num, $value) = ...;
        $HoA{NAME} = $name;
        $HoA{NUM}  = $num;
        push @{$HoA{VALS}}, $value;
}