What's the equivalent in Perl 6 to star expressions in Python?

Perl5:

sub drop_first_last { avg( @_[ 1 .. $#_-1 ] ) }     #this
sub drop_first_last { shift;pop;avg@_ }             #or this

Perl6:

sub drop_first_last { avg( @_[ 1 .. @_.end-1 ] ) }

sub drop_first_last(Seq() \seq, $n = 1) { seq.skip($n).head(*-$n) };
say drop_first_last( 1..10 );     # (2 3 4 5 6 7 8 9)
say drop_first_last( 1..10, 2 );  # (3 4 5 6 7 8)

The way it works: convert whatever the first argument is to a Seq, then skip $n elements, and then keep all except the last $n elements.

Use a slice.

sub drop_first_last (@grades) {
    return avg(@grades[1..*-2])
}