interpreter functions

abort — stop evaluation.
break — exit evaluation loop.
continue — continue evaluation in loop.
for — for loop.
function — function declaration.
if — conditional statement.
iskeyword — Returns all Nelson keywords.
keyboard — Stops script execution and enter in debug mode.
max_recursion_depth — Internal limit on the number of times a function may be called recursively.
parsefile — Parse a Nelson file.
parsestring — Parse a string.
switch — switch statement.
try — try/catch statement.
while — while loop.