CLtL2 Reference 

macro PIF : (condition action else-action)

macro PWHEN : (condition &body body)

macro PUNLESS : (condition &body body)

PIF, PWHEN and PUNLESS are the SubL procedural variants of if, when and unless from Common Lisp. For each, the condition argument must be a functional construct. Also, PIF takes exactly three arguments, making the action and else-actions identical in form.

macro FIF : (condition true-value false-value)

macro FWHEN : (condition true-value)

macro FUNLESS : (condition false-value)

FIF, FWHEN and FUNLESS are the SubL functional variants of if, when and unless from Common Lisp.

macro PCOND : (&rest clauses)

macro PCASE : (test-object &body clauses)

PCOND and PCASE are the SubL procedural equivalents of cond and case from Common Lisp.

Establishing New Variable Bindings Home Blocks and Exits