my $foo = [ {blah=>5,d=>1},
            {blah=>4,d=>2},
            {blah=>3,d=>3},
            {blah=>2,d=>4},
            {blah=>1,d=>5}];

my @bar = sort {$a->{blah} cmp $b->{blah} } @$foo;

print join(',',map {$_->{blah}} @bar), $/;