PERFORM Statement Variations

The simplest form, PERFORM PARAGRAPH-NAME, transfers control to a named paragraph or section, executes every statement in it, and then returns control to the statement immediately after the PERFORM once the paragraph falls through to its end. PERFORM FIRST-PARA THRU LAST-PARA executes a contiguous range of paragraphs as a single logical unit, which was the traditional way to group several related paragraphs before in-line PERFORM blocks became common; the range is defined purely by physical source order, so inserting a new paragraph between FIRST-PARA and LAST-PARA silently pulls it into the range. This out-of-line style, where the performed code lives physically separate from the PERFORM statement itself, is a defining characteristic of traditional COBOL structure and differs from the in-line PERFORM available in later standards.

PERFORM PARAGRAPH-NAME n TIMES executes the named paragraph exactly n times, where n can be a literal or a numeric data item evaluated once at the start of the loop, making it the direct equivalent of a fixed-count for-loop in other languages. Because the iteration count is fixed at loop entry, changing the value of the counting field inside the loop body has no effect on how many more times the loop will run, which is a common source of confusion for programmers coming from languages where loop bounds are re-evaluated every iteration. PERFORM TIMES has no built-in index variable, so if you need to know which iteration you're on, you must maintain and increment your own counter field inside the loop body.

PERFORM ... UNTIL condition repeats the named paragraph or in-line block while the condition is false, stopping as soon as it becomes true, making it COBOL's general-purpose conditional loop equivalent to a while-loop. By default, PERFORM UNTIL uses WITH TEST BEFORE behavior implicitly, checking the condition before each iteration, which means the loop body may execute zero times if the condition is already true on entry. Adding WITH TEST AFTER changes this to a do-while style, evaluating the condition after each execution of the loop body, guaranteeing the body runs at least once, which is the correct choice for patterns like reading the first record before checking for end-of-file.

An in-line PERFORM places the loop body directly between the PERFORM statement and its END-PERFORM scope terminator, rather than referencing a separately named paragraph, which keeps small loops self-contained and avoids polluting the PROCEDURE DIVISION with single-use paragraph names. In-line PERFORM works with every variation, TIMES, UNTIL, and VARYING, and is generally the preferred modern style because the loop's logic is visible in one place instead of requiring the reader to jump to a separately defined paragraph. The trade-off is that an in-line PERFORM cannot be invoked from elsewhere in the program the way a named paragraph can, so out-of-line PERFORM is still appropriate when the same logic needs to be reused from multiple call sites.