Iterate through and modify data in a feature class using ModelBuilder

Question

Using ArcGIS Pro 3.1.0

I'd like to create a model that iterates through features and modifies fields based on a logical if-statement. Specifically, I'd like to check if each field begins with number, and if it does, add a prefix to the field. Here's what I have in ModelBuilder so far:

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I input the sample data, use Iterate Feature Selection to pick individual features, and use a logical If Field Value Is statement to check if the first character of the field is a numeric value (0-9). This logical statement is a precondition for Calculate Field, which adds the desired prefix to the field.

My sample data:

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When I verify and run this model, regardless of what logical statement I use, Calculate Field runs against every feature in Sample_Data:

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Why isn't the precondition preventing the Calculate Field from running?

Answer 1

The tool just needs to be this:

Calculate Field tool

In this example it prefixies all text starting with a number character with "BBB"