Search a list

my @haystack = <Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo>;
 
for <Washington Bush> -> $needle {
    say "$needle -- { @haystack.first($needle, :k) // 'not in haystack' }";
}

Output:

Washington -- not in haystack
Bush -- 4

Or, including the "extra credit" task:

my Str @haystack = <Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo>;

for <Washingston Bush> -> $needle {
    my $first = @haystack.first($needle, :k);

    if defined $first {
        my $last = @haystack.first($needle, :k, :end);
        say "$needle -- first at $first, last at $last";
    }
    else {
        say "$needle -- not in haystack";
    }
}

Output:

Washingston -- not in haystack
Bush -- first at 4, last at 7

The built-in method .first takes a smart-matcher, and returns the first matching list element.

The :k adverb tells it to return the key (a.k.a. list index) instead of the value of the matching element.

The :end adverb tells it to start searching from the end of the list.

If you plan to do many searches on the same large list, you might want to build a search hash first for efficient look-up:

my @haystack = <Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo>;

my %index;
%index{.value} //= .key for @haystack.pairs;

for <Washington Bush> -> $needle {
    say "$needle -- { %index{$needle} // 'not in haystack' }";
}