Task 1: "Last Word

Define sub last_word($string, $regexp) that returns the last word
matching $regexp found in the given string, or undef if the string does
not contain a word matching $regexp.

For this challenge, a "word" is defined as any character sequence
consisting of non-whitespace characters (\S) only. That means punctuation
and other symbols are part of the word.

The $regexp is a regular expression. Take care that the regexp can only
match individual words! See the Examples for one way this can break if
you are not careful.

Examples

last_word('  hello world',                qr/[ea]l/);      # 'hello'
last_word("Don't match too much, Chet!",  qr/ch.t/i);      # 'Chet!'
last_word("spaces in regexp won't match", qr/in re/);      #  undef
last_word( join(' ', 1..1e6),             qr/^(3.*?){3}/); # '399933'
"

My notes: cool question. Will have a go!


Task 2: "Rotate String

Given a word made up of an arbitrary number of x and y characters, that
word can be rotated as follows: For the ith rotation (starting at i =
1), i % length(word) characters are moved from the front of the string to
the end. Thus, for the string xyxx, the initial (i = 1) % 4 = 1 character
(x) is moved to the end, forming yxxx. On the second rotation, (i = 2) %
4 = 2 characters (yx) are moved to the end, forming xxyx, and so on. See
below for a complete example.

Your task is to write a function that takes a string of xs and ys and
returns the minimum non-zero number of rotations required to obtain
the original string. You may show the individual rotations if you wish,
but that is not required.

Example

Input: $word = 'xyxx';

Rotation 1: you get yxxx by moving x to the end.
Rotation 2: you get xxyx by moving yx to the end.
Rotation 3: you get xxxy by moving xxy to the end.
Rotation 4: you get xxxy by moving nothing as 4 % length(xyxx) == 0.
Rotation 5: you get xxyx by moving x to the end.
Rotation 6: you get yxxx by moving xx to the end.
Rotation 7: you get xyxx by moving yxx to the end which is same as the given word.

Output: 7
"

My notes: sounds like fun.  Nice question.