In primitive languages, variables had broad scope. For instance, an integer variable called IEMPNO might be used in one part of a Fortran subroutine to denote an employee social security number (SSN), but during maintenance work on the same subroutine, a programmer might accidentally use the same variable, IEMPNO, for a different purpose, and this could result in a bug that was difficult to trace. Block structure makes it easier for programmers to control scope.

In the following R5RS Standard Scheme