The following is an example of an external rewriting program rewrite.pl, used to change the prefix /home/ to /u/:
#!/usr/bin/perl $| = 1; while (<STDIN>) { s|^/home/|/u/|; print $_; }
In this example, the external expression function used to invoke rewrite.pl is as follows:
NameTrans fn="rewrite" path="$(external('rewrite.pl', $path))"