In classic COBOL, subroutines are implemented by the PERFORM... and PERFORM...THRU statements. They are not quite classic subroutines. They do not, for example, have local variables. They can be confounded by GOTO statements.
A good textbook on COBOL is pretty much an absolute necessity.
"COBOL! Why did it have to be COBOL?!"
-- Indiana Jones and the Temple of Computers