Can Singlish be understood by a foreigner?

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Well, its been a long time. I was talking to an executive from Barcelona, Spain recently and we happened to talk about languages (since my job is very much related to it). Though he knew English, he was expressing the difficulty he had in understanding some of his peers in the office. I wonder how many foreigners here faces the same challenge. Does anyone out there want to share about their experiences or give some references? It may help our overseas friends here...