VarExists can be used to check whether a variable has been defined in the script during the previous
execution steps or not.
Check whether the varilable exists
In this example the variable @notfound is not defined, therefore it will show the
message 'Variable not defined' during execution
IF VarExists(@notfound)=FALSE THEN
PRINT 'Variable not defined!'
PRINT 'Variable @notfound is defined'