A bit shorter but should still work okay: 
s/(\:)\s+/$1/

[download]
or just for fun: 
s/(:) +/$1/

[download]
Second probably has loads of reasons why it'll fall over in other cases but seems to work fine here.

In reply to Re^3: How can I strip an arbitary number of "inner" spaces from a string? by gothic_mallard
in thread How can I strip an arbitary number of "inner" spaces from a string? by habhab

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