end sub -- ends a subroutine definition

 
sub foo(...) 
  ... 
end sub 

Marks the end of a subroutine-definition (which starts with the sub-keyword). The whole concept of subroutines is explained within the entry for sub. 

print foo(3) 

sub foo(a) 
	return a*2 
end sub 

This program prints out 6. The subroutine foo simply returns twice its argument.