#!/usr/bin/perl -w

if (!defined($ENV{foo})) {
   if (@ARGV > 0 && $ARGV[0] eq 'nested') {
      die("Unable to find value for env var FOO\n");
   }

exec '/bin/csh', '-c', sprintf("source script1.csh ; perl $0 nested %s",join(" ",@ARGV));
   die("Unable to execute csh: $!\n");
}

printf "%s = %s\n",$_,$ENV{$_} foreach keys %ENV;