PunchCAD evaluates equations and formulas in the data boxes and performs actions (say, drawing a line of f(x) length) with the product, you don't have to copy the result into another box to use it.

There is some automatic conversion, because .dxf used imperial dimensions as Autodesk's bequest to the field, so the factor of 25.4 to to convert to mm is accommodated. Other conversions like cm to mm or metres, or imperial fractions to imperial decimals, aren't. I don't think that that sort of conversion is particularly useful or likely to be commonly used, because the various fields that the drawings and data are used in usually stick to the standards generally used within their discipline, like mm as the base unit for mechanical engineering, or metres for surveying or civil engineering. I probably mean the same thing as you do when I use the term 'data' boxes instead of 'text' boxes, because we're describing objects parametrically, using data. In CAD, text boxes are usually boxes that actual text goes into, for 2D sheet drawings.

if units in preferences is set to e.g. "millimeters" the input of other units in e.g. the length field of the line tool will yield the following results:

• '1m' = 1,000.0 mm
• '1cm' = 10.0 mm
• '1"' = 25.4 mm

hth,
Norbert