imrags,
I am confused. Are you looking for a fast way or are you looking for a way to write unmaintainable code that fits on 1 line? It is a huge mistake to think less code necessarily means faster.

You might want (untested):

my %uniq = map {$_ => $_} grep {length $_ > 4} @website;
@website = grep defined, @uniq{@website};
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