Huh, I've been doing Ruby since 2008 and I've never seen a block passed to gsub/gsub!. Neat! That said, a block isn't necessary here and the one-liner can be

Huh, I've been doing Ruby since 2008 and I've never seen a block passed to gsub/gsub!. Neat! That said, a block isn't necessary here and the one-liner can be even shorter: @sentence.gsub!(/\b\w/, &:upcase) &: call syntax is actually a little faster post 1.9, too.