No one has yet explained why this doesn't work as you expect.

Consider an array of three values:

my @to_clean = ( '', 1, 2 );

We'll loop through the array with indices. We'll make sure that the element at that position is defined, true, and not the empty string:

for my $i ( 0 .. $#to_clean )
{
    next if defined $to_clean[ $i ] and $to_clean[ $i ];
    next unless $to_clean[ $i ] eq '';
}
[download]

Here's where it gets tricky. By spliceing, you're changing the original array.

splice( @to_clean, $i, 1 );

After the first loop, we'll splice out the empty string at index zero. The array will then contain 1 and 0 2. Unfortunately, $i will be 1 on the next loop iteration, and it won't check the 0th element again.

You could mess with redo. You could push the elements you want to keep on a secondary array. It's unlikely you'll come up with anything simpler or faster than grep though.

Update: This lets undef through, but it catches zero. It's just an example, though.