Now there are two passes over the list, and the situation isn't going to get any prettier from here. What you want is basically a histogram of the data, and you can get that with a hash:

    my %histogram;
    $histogram{$_}++ for @list;

This hash associates each individual item with its count, and it only traverses the list once.

In a recent case, I was looking at a list of tags associated with various photographs. To lay out the data for display, it was useful to know how many different tags there are in the list. I could get that simply from the number of keys in the histogram:

    $unique = keys %histogram;

I could also delete the duplicates and end up with a list of the unique tags:

    @unique = keys %histogram;