This works:

# salt salt-test file.replace path=/usr/local/etc/nrpe.cfg pattern='allowed\_hosts\=127\.0\.0\.1' repl='allowed_hosts=10.55.0.3'


This does not, and I don't know why:

nrpe:
  pkg:
    - installed
  service.running:
    - name: nrpe2
    - enable: True
    - watch:
      - file.replace:
        - path: /usr/local/etc/nrpe.cfg
        - pattern: allowed_hosts=127.0.0.1
        - repl: allowed_hosts=10.55.0.3

# salt salt-test state.highstate -vvvv
Executing job with jid 20131211211639444633
-------------------------------------------

salt-test:
    Data failed to compile:
----------
    Illegal requisite "[OrderedDict([('path', '/usr/local/etc/nrpe.cfg')]), OrderedDict([('pattern', 'allowed_hosts=127.0.0.1')]), OrderedDict([('repl', 'allowed_hosts=10.55.0.3')])]", please check your syntax.