Now that you've gotten the necessary lectures about why you shouldn't be doing this, here is a way to do specifically what you asked for (even though I think the insertion of the space is a mistake more often then not, so I would be inclined to leave out the added space): 
sub cap
{
    local $_ = shift || '';
    s/\b(\w\S*)/\u\L$1/g;
    s/(?<=\bO')(\w)/\u$1/g;
    s/(?<=\bMc)(\w)/ \u$1/g;
    return $_;
}

[download]
Since that uses zero-width look-behind, which has to involve a fixed number of characters to match, you'd have to add another separate regex to handle the case of "Mac..." (that is, just adding "a?" to the last regex above would cause a run-time error).

In reply to Re: Capitalization Case Help! by graff
in thread Capitalization Case Help! by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.