While this is amazing, I should point out that for most languages he only needs to understand enough syntax to print strings and possibly unquote them. If you actually run this program into the first language, Ruby, the actual code (meant to be a Rust code) is as follows:

    fn main(){print!("{}",("object QR extends App{print(\"(display \\\"printf(\\\\\\\"1d;s/.//;s/1/ the sum of a son and0/g;s/0/ twice/g;s/2/You are as bad as/g;s/3/ a son!Speak your mind!/g\\\\\\\\n#The Relay of Quine.\\\\\\\\n#Ajax, a man.\\\\\\\\n#Ford, a man.\\\\\\\\n#Act i: Quine.\\\\\\\\n#Scene i: Relay.\\\\\\\\n#[Enter Ajax and Ford]\\\\\\\\n#Ajax:\\\\\\\\n#\\\\\\\");function[]=f(s);for i=1:2:length(s),printf(\\\\\\\"2%s3\\\\\\\",part(dec2bin(hex2dec(part(s,i:i+1))),$:-1:2)),end;endfunction\\\\nf('[lots of hexdump]')\\\\nf('[lots of hexdump]')[snip]\\\\nprintf(\\\\\\\"\\\\\\\\n#[Exeunt]\\\\\\\");quit\\\")\");}"));}

...where `("object ... ;}")` part is a single string literal here. The actual quine stuff can be done in just one language at your choice, or can be assimilated into some other language where unquoting is a bit heavier. It is much easier than polyglots, where a single code should be interpreted in multiple languages.