Hopefully I can break this down in a little better explaination.

/"([^"]*)"/

1. [^"] is a negated character class. Which means 'any character except (")'.

2. [^"]* Your regex wants 'zero or more (*)' of that negated character class.

3. /"([^"]*) then your regex wants 1 double quote at the beginning of a match (not the line)

4. /"([^"]*)"/ then your regex wants 1 double quote at the end of the match

Ok now lets break down what happens with your string "hello"you"

" Your first character. Your regex is happy it matches number 3

hello" Your regex clicks along happily down the next 5 non-double quotes till it sees ". Oops this breaks rule number 1.

hello Your regex moves back one click. It is happy again it matches number 2

"hello" Your regex moves forward one click to match number 4.

You regex is happy and matches all 4 of your rules

If you apply this to your other regex /^"([^x]*)"$/ you can see why your examples work

HTH

grep

grep> cd /pub grep> more beer