From the manual
4.13. Multi-statement Lines

In order to allow more compact programs and logical grouping of related commands, PBP supports the use of the colon ( : ) to separate statements placed on the same line. Thus, the following two examples are equivalent:

W2 = W0
W0 = W1
W1 = W2

is the same as:

W2 = W0 : W0 = W1 : W1 = W2
This does not, however, change the size of the generated code.