perl -MData::PowerSet -le 'my $p = Data::PowerSet->new(qw(A B C D E)); print "@$_" while $_= $p->next'
# produces :
A B C D E
B C D E
A C D E
C D E
A B D E
B D E
A D E
D E
A B C E
B C E
A C E
C E
A B E
B E
A E
E
A B C D
B C D
A C D
C D
A B D
B D
A D
D
A B C
B C
A C
C
A B
B
A