Pull with regex

test.js

MongoDB shell version: 1.8.1
connecting to: test
> db.test.insert({ _id:3, "items": [ 'appstore.com', 'engineapp.com', 'asp.ca' ] })
> db.test.find()
{ "_id" : 3, "items" : [ "appstore.com", "engineapp.com", "asp.ca" ] }
> db.test.update({}, {$pull : { items: {$regex: 'app' } } })
> db.test.find()
{ "_id" : 3, "items" : [ "asp.ca" ] }

test2.js

MongoDB shell version: 1.8.1
connecting to: test
> db.test.insert({ _id:3, "items": [ 'appstore.com', 'engineapp.com', 'asp.ca', /app/ ] })
> db.test.find()
{ "_id" : 3, "items" : [ "appstore.com", "engineapp.com", "asp.ca", /app/ ] }
> db.test.update({}, {$pull : { items: /app/ } })
> db.test.find()
{ "_id" : 3, "items" : [ "appstore.com", "engineapp.com", "asp.ca" ] }

version()
version: 1.8.1
db.test.find()
{ "_id" : 974978785, "aliases" : [
"http://even-home.appspot.com/",
"http://twitter.com/zjf1119",
"http://twitter.com/account/redirect_by_id?id=101147112"
], "confidence" : 50, "source" : 1 }
{ "_id" : 83911156, "aliases" : [
"http://twitter.com/account/redirect_by_id?id=53921636",
"http://xreamblog.appspot.com/",
"http://twitter.com/xream"
], "confidence" : 50, "source" : 1 }
{ "_id" : 942476775, "aliases" : [
"http://twitter.com/account/redirect_by_id?id=19028049",
"http://samdeha.appspot.com/",
"http://www.quora.com/zhao-zhou",
"http://twitter.com/xueyufan"
], "confidence" : 50, "source" : 1 }
db.test.update({}, {$pull : { aliases: {$regex: '.*appspot.com' } } })
db.test.find()
{ "_id" : 974978785, "aliases" : [
"http://twitter.com/zjf1119",
"http://twitter.com/account/redirect_by_id?id=101147112"
], "confidence" : 50, "source" : 1 }
{ "_id" : 83911156, "aliases" : [
"http://twitter.com/account/redirect_by_id?id=53921636",
"http://xreamblog.appspot.com/",
"http://twitter.com/xream"
], "confidence" : 50, "source" : 1 }
{ "_id" : 942476775, "aliases" : [
"http://twitter.com/account/redirect_by_id?id=19028049",
"http://samdeha.appspot.com/",
"http://www.quora.com/zhao-zhou",
"http://twitter.com/xueyufan"
], "confidence" : 50, "source" : 1 }

So it worked.

The following entry was updated: "_id": 974978785
Notice how "http://even-home.appspot.com/" is now gone?

Of course, it did not update all documents because you did not set the "multi" flag to true.