Regex with digits and some special characters

Question

I need help with creating a regex that would recognize tokens in text.
Token requirements are as follows:

• should start and end with $
• can contain any combination of letters, digits, _
• can contain only one consecutive . , meaning:
  • $some.valid.sample$ is valid
  • $some..invalid.sample$ is not
• can contain square brackets, but only if they contain a number inside, meaning:
  • $some.valid[0].sampl$ is valid
  • $some.invalid[].sample$ is not
• contains between 1 and 64 characters

additional requirements (after discussion in comments):

• square brackets with number have to be followed by . if they are not at the end (ie if they are not just before closing $ )
• length constraint applies to content between two $

Can anyone help me out with this?
So far I have \\$([A-Za-z0-9._]*(\\[\\d+\\])*)+]$

Answer 1

根据注释中更新的规则，这是您需要的：

\$(?=[^\$]{1,64}\$)\w+(?:\[\d+\])?(?:\.\w+(?:\[\d+\])?)*\$

Answer 2

How about this pattern:

\$\w+?.?\w*?(\[\d+\]?)?.?\w*?\$

You can test it here

it is a little too narrow though. I would take the suggestion by @Wiktor Stribizew