If it were my surname you were mauling, I'd be more than a bit annoyed. I get enough of my surname's Anglicised (actually Brazilinated, but it's close enough) form being auto-"corrected" into the original Russian. I am actually capable of spelling it correctly, and I do just that.

That said, you could

$surname =~ s/^((?:Mc|Mac|De|Da|Du)?)(.*)$/\u\1\u\2/i;
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(assumes the surname starts off lower-cased).

Other problems: not smart enough. E.g. <samp>'mack'</samp> becomes <samp>'MacK'</samp>, which is wrong; you might want .{3,} instead of .* in the regexp.

But I really don't think you should be doing this...