In PowerShell I've been trying different ways of stripping out all characters from a WinForms textbox other than the pattern I need and I cannot come up with a better solution for what I'm after; I am learning regex and need some guidance. This feels basic to me but I feel like I'm missing something obvious. I'm using the textbox's TextChanged event to prevent illegal characters from being typed and I have (what feels like) a bloated solution.

Goal:

• User allowed to type a single leading dollar sign followed by up to 6 chars from [A-V0-9]
  • If no $ is typed, the first legal character typed should produce a leading $ followed by said legal character (typing A will produce $A in the textbox)
  • If an illegal character is typed first, no leading $ should be produced in the textbox
• Illegal characters won't show up in the textbox
• Pasted text is processed/stripped as efficiently as possible
• The last character deleted will also delete the remaining $
  • If textbox shows $T and user backspaces the T leaving a single $, the remaining $ will also be deleted

Pasting into the textbox examples:

• $$-#AZY$B9=% would become $AB9
• Z))