Add anchors

[alecramsay]

P. 42:

• ^ : start of line
• $ : end of line
• \A : start of string
• \Z : end of string (with or without trailing newline)
• \z : end of string (very end)

First two are done.

[alecramsay]

Second two are done.

Is the last (or the second to last) a power user feature, i.e., just write the regex?