Algorithm::ChooseSubsets does this. The output follows __END__.

use strict; 
use warnings; 
use Algorithm::ChooseSubsets; 

my @items = qw/red white blue/;
my $iter = Algorithm::ChooseSubsets->new(\@items); 
while (my $x = $iter->next) { 
     print "@$x\n"
}

__END__
C:\perlp>perl t2.pl

red
white
blue
red white
red blue
white blue
red white blue

C:\perlp>
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Chris