While almost all f77 code works with the f90 and f95 compilers, the opposite is not true. If the modern syntax or array assignment options are used in f90 and f95, the code cannot be compiled using f77. Take your pick since both are endorsed by Perl's creator, Larry Wall. Perl is the standard for scripting as well as building programs in a short amount of time. For example, many web sites, including the Atm web site use Perl to process data and prepare it for users.
Many excellent books are also available.