You might want to consider a negative lookahead on \d as well:

\d{4}-\d{1,3}(?![-\d])
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Of course, this means you won't match a string like "2005-1222" either. The original would match that, and if that's intentional, you need an even trickier version:

\d{4}-\d{1,3}(?!\d*-)
[download]

Here's betting one of these should be what you want. :-)