[plt-scheme] How to use (load path) in plt-scheme?

I use plt-scheme as my shell scripts language. I will run some other
tools to generate some variables dynamically, and load them into
scheme. But my scripts fails.

My script looks like this:

foo.scm :
#!/usr/bin/scheme
#!scheme
(require scheme/system)
(system "echo (define bar \"Hello world\n\") > variables.scm")
(load "variables.scm")
(display bar)