Solution 

• Version 8

#!/usr/bin/perl -nlp
/\./;
@h{$_,"$`.M"}=1;
}$_=join($\, sort keys %h);{

• perl -p - assume loop like -n but print line also, like sed

• in conjuction with }{ (whatever that is)?

• seems to be some sort of source code filter

• big hack #2!