....um...er.... not quite or, at least, not always:

s/(the most important factor in deciding which train to take isn't the speed of the train, but whether it brings me to where I want to be)/\1 when I want to get there./

Sometimes, the [bicycle|car|plane] is the right choice (cf Moritz advice re letting the database do some of the work).

Update:   AnomalousMonk (thanks!) notes: s/(...)/$1 when I want to get there./ vice s/(...)/\1 when I want to get there./ : capture variable is preferable to backreference in string interpolation (backreference generates warning).