Add substring to specific conditions

Hello everybody
I have some data in Column H
Some data like that pattern

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11 or 12 digits then a character then 11 or 12 digits

If this pattern existed then using udf or formula to add the following substring

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which represents a character and 4 digits

The substring to be added after the first 11th or 12th digits and before the character existed
and the same substring to be added at the end

The result should be

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Hope the example is clear
I will attach a sample