[gnulinux]

    All words starting with the letter "n" and ending with "g", case insensitive
    >> /^nw*g$/i

This is not right. That should be a "\w" instead of "w".

[curiousgal]

Same with the last one, it should be \d instead of d. Seems like an escape character issue.

[emilfihlman]

It's otherwise wrong, too. It shouldn't have ^ or $, and \w matches non word characters. It should be /n[a-z]*g/gi