Used if you need a simple chmod+s on a script. Compile a simple c app and then set it to chmod+s and then your script will run as the specified user.
Sample code:
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
int main(void)
{
execl("/usr/bin/svn", "svn", "export", "http://foo.bar/", "--username",
"dtbaker", "--password", "bar",
"/var/www/path/to/somewhere/", "--force", (const char *) NULL);
return(EXIT_FAILURE);
}