ちょーてきとーだけど、pythonで書いてみた(･∀･)
#!/usr/local/bin/python
import poplib, os
M = poplib.POP3("pop3.mail.server")
M.user("username")
M.pass_("password")
numMessages = len(M.list()[1])
for i in range(numMessages):
  body = []
  eoh = 0
  for j in M.retr(i+1)[1]:
    if eoh == 0:
      if j == "":
        eoh = 1
      elif j[0:8].upper() == "SUBJECT:":
        if j.find("This Is Script") == -1:
          break
    else:
      body.append(j + "\n")
  else:
    M.dele(i+1)
    f = open("tmp.py", "w")
    f.writelines(body)
    f.close()
    os.system("python tmp.py")
M.quit()