[From string (line 6) ]                           
                                                  
@startuml                                         
!function $upper($a)                              
	!$len = %strlen($a)                              
	!$pos = 0                                        
	!$z = ""                                         
...                                               
... ( skipping 52 lines )                         
...                                               
	!elseif $x == "z"                                
		!$x = "Z"                                       
	!endif                                           
	                                                 
	!if %substr("-" + $a, $pos, 2) == "\n"           
		!$x = "n"	                                      
		John -> Sally : I found a "\n" at position $pos!
	!endif                                           
	                                                 
	!$z = $z + $x                                    
	!$pos = $pos + 1                                 
!endwhile                                         
!return $z                                        
!endfunction                                      
                                                  
John -> Sally : $upper("hello")                   
	!$len = %strlen($a)                              
	!$pos = 0                                        
	!$z = ""                                         
!while ($len-$pos) > 0                            
^^^^^                                             
 Parsing syntax error about $len-$pos