(CommandList
  children: [
    (Pipeline
      children: [
        (C {(dpkg)} {(--list)})
        (C {(awk)} {(SQ <"{print $2}">)})
        (C {(grep)} {(linux-headers)})
        (C {(xargs)} {(apt-get)} {(-y)} {(purge)})
      ]
      negated: False
    )
    (C {(apt-get)} {(-y)} {(purge)} {(ppp)} {(pppconfig)} {(pppoeconf)})
    (C {(apt-get)} {(-y)} {(purge)} {(popularity-contest)})
    (C {(apt-get)} {(-y)} {(autoremove)})
    (C {(apt-get)} {(-y)} {(clean)})
    (C {(rm)} {(id_rsa.pub)})
    (C {(rm)} {(VBoxGuestAdditions-) (Lit_Other "*") (.iso)})
    (C {(rm)} {(.vbox_version)})
  ]
)