By default, spaces are seen as regular characters and are included in variable assignments.  E.g. The following line..
 
Let>a = 5
 
.. would create a variable called "a " with the value " 5".
 
Normally, therefore, you should use:
 
Let>a=5
 
But experienced programmers are used to the language ignoring spaces.  This can be achieved by setting IGNORESPACES to 1:
 
Let>IGNORESPACES=1
Let>a = 5
 
This would set variable "a" to the value 5.
 
If spaces are ignored then strings that need preceding spaces will need to be delimited.  To do this use {"string"}
 
Try stepping through the example below with the Debugger and Watch List open.  

Example
 
Let>VAREXPLICIT=1
Let>IGNORESPACES=1
 
Let>a = 5
Let>b = 22
 
Input>c, Enter a number:, 0
If> %c% > 0
 Let> d = {%a% + %b% * %c%}
Else
 Let> d = {%a% * %b%}
Endif
MessageModal> Answer: %d%
 
//With IGNORESPACES=1 do the following if you want leading/trailing spaces in a string
Let>string_with_spaces = {"  I want preceding spaces  "}
MessageModal> %string_with_spaces%
 
//Or just switch IGNORESPACES off and on
Let>IGNORESPACES=0
MessageModal>  Need these leading spaces
Let>IGNORESPACES=1
 
//Inline Expressions:
MessageModal>{"  I want preceding spaces"}
 
//Sum:
MessageModal>{5 + 4}
 
//Embed a complex expression within the string as you would a variable:
MessageModal>W Pos: %{Pos("W","Hello World")}%