Problem 1035. Generate a vector like 1,2,2,3,3,3,4,4,4,4

how to understand the part of .'';)?

This solution uses match-time code evaluation for regular expressions to reduce the solution size to 10. '' in a character array represents a literal ', so in the actual code you get a .'; where .' is transposition (remember that ' without the dot is the complex conjugate transpose).