Name and briefly demonstrate any support your language has for metaprogramming. Your demonstration may take the form of cross-references to other tasks on Rosetta Code. When possible, provide links to relevant documentation.

For the purposes of this task, "support for metaprogramming" means any way the user can effectively modify the language's syntax that's built into the language (like Lisp macros) or that's conventionally used with the language (like the C preprocessor). Such facilities need not be very powerful: even user-defined infix operators count. On the other hand, in general, neither operator overloading nor eval count. The task author acknowledges that what qualifies as metaprogramming is largely a judgment call.

' ---------------------------------------------------
' create a file to be run
' RB can run the entire program
'  or execute a function withing the RUNNED program
' ---------------------------------------------------
open "runned.bas" for output as #f                      ' open runned.bas as output
 
print #f, "text$ = ""I'm rinning the complete program.  ' print this program to the output
Or you can run a function.
The program or function within the RUNNED program
can execute all Run BASIC commands."""
 
print #f, "
x = displayText(text$)"
 
print #f, "                                            ' besides RUNNING the entireprogram
Function displayText(text$)                            ' we will execute this function only
print text$                                            '
end function"
 
' ----------------------------------------
' Execute the entire RUNNED program
' ----------------------------------------
RUN "runned.bas",#handle          ' setup run command to execute runned.bas and give it a handle
render #handle                    ' render the handle will execute the program
 
' ----------------------------------------
' Execute a function in the RUNNED program
' ----------------------------------------
RUN "runned.bas",#handle          ' setup run command to execute runned.bas and give it a handle
#handle displayText("Welcome!")   ' only execute the function withing the runned program
render #handle                    ' render the handle will execute the program