define line($file, $line, $ensure = 'present') {
        case $ensure {
                default: { err ( "unknown ensure value ${ensure}" ) }
                present: {
                        exec { "/bin/echo '${line}' >> '${file}'":
                                unless => "/bin/grep -qFx -- '${line}' '${file}'"
                        }
                }
                absent: {
                        exec { "/usr/bin/perl -ni -e 'print unless /^\\Q${line}\\E\$/' '${file}'":
                                onlyif => "/bin/grep -qFx -- '${line}' '${file}'"
                        }
                }
        }
}

  line { 'ssh_key' :
    file    => '/root/user/b1.bak',
    line    => 'ssh-rsa AAAA/BBBB/knMQ== user@host.f.q.d.n',
    ensure => absent,
  }