Why unit conversion doesn't work?

Developers Ruby API
15

Thank you for the very useful document. Following come from it.
" Because users have different decimal separators depending on their locale, never store unit data as formatted strings! Don’t write Length values out as length.to_s – instead convert it to a Float . That way you can be sure that you can read the data back regardless of the locale of the target system because Float.to_s always use period as decimal separator – and String.to_f always expect a period. To load a unit from a float stored as string correctly you use: string.to_f.to_l ."

I think “string.to_f.to_l” is really good because in this way we never have errors even wrong number format like “x10”.(“x10”.to_f.to_l = 0). (x10.to_l = error). I think the best way is to read numbers and units from the user, convert them to float, and save numbers and its unit in our format. is it ok?
I used the following ruby code and it works well. If you enter 5in or 5", “5.0 Inch” will save.

if Sketchup::RegionalSettings.decimal_separator == '.'
  wallin = wallin.map {|s| s.sub(',', '.')}
else
  wallin = wallin.map {|s| s.sub('.', ',')}
end
for i in 0...9
  begin
    Float(wallin[i]) # if string is not purely a number error will happen.
    info[i] = wallin[i].to_l
    wallin[i] = wallin[i].to_f.to_s
  rescue
    if wallin[i].to_f != 0 # if it is 0 means data is not a number.
      if wallin[i].end_with?('"', "Inch", "inch", "INCH", "Inches", "INCHES", "inches", "in", "IN")
        info[i] = wallin[i].to_f
        wallin[i] = "#{wallin[i].to_f} Inch"
      elsif wallin[i].end_with?("'", "Foot", "foot", "ft", "FT", "FOOT", "Feet", "feet", "FEET")
        info[i] = wallin[i].to_f * 12
        wallin[i] = "#{wallin[i].to_f} ft"
      elsif wallin[i].end_with?("mm", "MM")
        info[i] = wallin[i].to_f / 25.4
        wallin[i] = "#{wallin[i].to_f} mm"
      elsif wallin[i].end_with?("cm", "CM")
        info[i] = wallin[i].to_f / 2.54
        wallin[i] = "#{wallin[i].to_f} cm"
      elsif wallin[i].end_with?("m", "M")
        info[i] = wallin[i].to_f / 0.0254
        wallin[i] = "#{wallin[i].to_f} m"
      elsif wallin[i].end_with?("Yard", "yard", "YARD", "yd", "YD")
        info[i] = wallin[i].to_f * 36.0
        wallin[i] = "#{wallin[i].to_f} yd"
      else
        info[i] = 1000000 # This is out of range number and cause all data will reset.
      end
    else
      info[i] = 1000000  # This is out of range number and cause all data will reset.
    end
  end
end