10 Solve problems with tools you know
20 Learn new tools
30 GOTO 10
Sure, but since learning new tools more than superficially means solving problems with them, that is equivalent to:
10 Solve problems with tools you know
20 Solve problems with tools you don't yet know
30 GOTO 10
And learning new tools -- programming languages specifically here -- often involves learning new techniques, that while not necessarily as natural and popular with your current language, can be applied there, which its good to have in your pocket for when the techniques that are most popular/natural with your current languages aren't great for solving a problem you run into.
There are good reasons that the The Pragmatic Programmer includes the recommendation to learn a new language every year.
There are good reasons that the The Pragmatic Programmer includes the recommendation to learn a new language every year.