variable substitution

in the new way of PSL:

cla$=do("Get label of interval...", 4,1) 
printline 'cla$' 

this does not work:

Found a numeric expression instead of a string expression. 
Formula not run. 
Script line 1 not performed or completed: 
« cla$=do("Get label of interval...", 4,1) » 
Menu command "Run" not completed.

Which is true because if you switch the variable from cla$ to cla, it works, returns 'undefined'. 

You can do it the old way, which works: 

cla$=Get label of interval... 4 1 
printline 'cla$' 

by the way, this works with arrays too (it seems numeric array behaves rather normally in the old way of scripting): 

Therefore, basically there is an asymmetry between functions that return a number vs. a string, because both return numeric values in the do("Get...",x,y)mode. This will work with variable assignment if it is meant to return a number, naturally: 

numOfIntWordTier=do("Get number of intervals...", tierLyrics+1)