my %complete_list;
my @groupID_order;

for my $rec ( @records )
{
    # do prep-work on $rec as needed to create returnable rec, then:

    my $groupID = $rec->{ID}
    push @groupID_order, $groupID unless exists( $complete_list{$groupID} );

    push @{$complete_list{$groupID}}, $usable_rec;
}

my @return_array;

for my $groupID ( @groupID_order )
{
    # maybe you want to work on creating header stuff here for each group, then:

    push @return_array, $header_rec,  @{$complete_list{$groupID}};
}

return \@return_array;