There's here, for example, given text:

 WASP-41b 0.94 1.18 3.052404 0.04 1244 transit 590 0.93 5545
 
 WASP-42b 0.527 1.122 4.9816819 0.0561 transit 520 0.95 5315
 
 WASP-47b 1.21 1.15 4.16071 0.052 1275 transit 650 1.11 5576
 
 WASP-49b 0.378 1.115 2.7817387 0.0379 transit 550 0.94 5600
 
 WASP-52b 0.46 1.27 1.7497798 0.0272 transit 460 0.87 5000
 
 WASP-54b 0.636 1.653 3.6936411 0.04987 transit 650 1.21 6100
 
 WASP-55b 0.627 1.335 4.4656291 0.0558 1290 transit 1100 1.16 6070
 
 WASP-56b 0.571 1.092 4.617101 0.05458 transit 830 1.03 5600
 
 WASP-57b 0.644 1.05 2.83891856 0.03769 transit 1480 0.89 5600

Want to modify `buffer` text around given marked `region` with some character, turning it as:


 WASP-41b 0.94 1.18 3.052404 0.04 1244 transit 590 0.93 5545
 
 WASP-42b 0.527 1.122 4.9816819 0.0561 transit 520 0.95 5315
 
 WASP-47b 1.21 1.15 4.16071 0.052 1275 transit 650 1.11 5576
 *********************************************** 
 WASP-49b 0.378 1.115 * 2.7817387 0.0379 transit 550 * 0.94 5600
 * * 
 WASP-52b 0.46 1.27 * 1.7497798 0.0272 transit 460 * 0.87 5000
 * * 
 WASP-54b 0.636 1.653 * 3.6936411 0.04987 transit 650 * 1.21 6100
 * * 
 WASP-55b 0.627 1.335 * 4.4656291 0.0558 1290 transit 1100* 1.16 6070
 *********************************************** 
 WASP-56b 0.571 1.092 4.617101 0.05458 transit 830 1.03 5600
 
 WASP-57b 0.644 1.05 2.83891856 0.03769 transit 1480 0.89 5600

That seems to be very simple, but would like to know how to do it.

Any idea?