Sure but if you use like five languages then the differences between s.length len(s) and length(s) will blur when at the beginning of the day you need to refresh the cache for todays language.
i could memorize them all but it is less interesting than reading papers about optimizing algorithms for cloud economics or other more valuable (to me) ideas.
Why are you using five languages? I mix them up when I switch, but I rarely work in more than two languages at once, and keeping two separate isn't that hard.
When I'm working in my preferred environment, I need to work in its language, but the language/VM is built in something (usually C), and the kernel I'm running on is built in something (usually also C), and I might be making a webpage where I need a bit of Javascript. And sometimes I need to poke at a shell script or something that's overgrown shell and is now Perl. And sometimes my preferred environment isn't really the right fit for the problem at hand, so I've got to use something else. Oh, and maybe I need to compile stuff, so here comes Make.
Context switching between Java, SQL, Javascript and a build scripting language isn't _that_ unusual an experience. Throw in a templating language there and you're at 5.
i could memorize them all but it is less interesting than reading papers about optimizing algorithms for cloud economics or other more valuable (to me) ideas.