The single quote is written with: ' ' (2 quotes).
When defining a constant, the latter must be enclosed by single quotes (eg 'SSS'). Then, to set a variable with a quote, use four quotes.
Example
Example 1:
W_VAR = ''''
Example 2: assigning a text enclosed by quotes in a variable:
VAR = '... text ..' // '''' // VAR1 // '''' // '..text ..'