my @set = ('A' .. 'Z', 0 .. 3);
my $min = 3;

my @result;

for my $begin (0 .. $#set-$min+1) {
    for my $end ($begin+$min-1 .. $#set) {
        push @result, "@set[$begin .. $end]";
    }
}

{
    local $" = ''; # interpolate an array without spaces
    print "$_\n" for @result;
}