String replace with rules
I used this for my incoming feeds, changing http:// to https://

{ "rules_http_to_https" : {
    "LABEL" : "http to https",
    "PLUGIN" : "reaction rule",
    "ACTIVE" : false,
    "OWNER" : "rules",
    "REQUIRES" : [ "php", "rules", "feeds" ],
    "ON" : { "feeds_import_canada_com" : [] },
    "DO" : [
      { "data_set" : {
          "data" : [ "node:body:value" ],
          "value" : "\u003C?php\r\necho str_replace(\u0022http:\/\/\u0022 , \u0022https:\/\/\u0022, \u0022[node:body]\u0022 );\r\n?\u003E"
        }
      },
      { "data_set" : {
          "data" : [ "node:field-contestpageurl" ],
          "value" : "\u003C?php\r\necho str_replace(\u0022http:\/\/\u0022 , \u0022https:\/\/\u0022, \u0022[node:field-contestpageurl]\u0022 );\r\n?\u003E"
        }
      }
    ]
  }
}