Validate Alphanumeric characters in an input field

Hi 

I am working in version 19.3.

I have two requirements:

1. In a text field, user is able to enter only alphanumeric characters and no special characters. 

    For eg: User can enter the values- 1235678901, 12A3178R9, 12ru38901, u189132W9

2. In a text field, user can enter alphanumeric value of the form: 2 alphabets, 6 numbers, 1 alphabet. For eg: AG124567UP, ar781329kw, yT893052eR

I need to put validations on my text field, if user enters rather than expected values in both the cases.

If I had the restriction that user can enter only numeric value in the text field, then I would have used stripwith():

a!localVariables(
  local!inputValue,
  a!textField(
    label:"Test Value",
    value:local!inputValue,
    saveInto:local!inputValue,
    validations: if(
      rule!APN_isBlank(local!inputValue),
      "",
      if(
        rule!APN_isBlank(stripwith(local!inputValue,"1234567890")),
        "",
        "The value provided is not a valid number"
      )
    )
  )
)

Any suggestions please.

Thanks in advance!!