quotes inside quotes

taken from tip 85 of the very good book 'Practical Vim: Edit Text at the Speed of Thought' ! I'd be interested what people use :)

Input

This string contains a 'quoted' word.
This string contains 'two' quoted 'words.'
This 'string doesn't make things easy.'

Output

This string contains a "quoted" word.
This string contains "two" quoted "words."
This "string doesn't make things easy."