htaccess REGEX to accept a particular set of characters in URL

I have a particular set of characters that i want to mark as acceptable:

a-z,A-Z,0-9,*,%,/,\,_.

Now i am being able to create an .htaccess file that enables this for:

a-z,A-Z,0-9,_,

but the rest of the characters are not working. The url is giving a 404 error. here is the regex i am using

[a-zA-Z0-9_]

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PS- I have check many of the SO questions related to htaccess, but my problem is not solved. These were helpful, but whenever i try to add the remaining characters in the CHARACTER SET of my regex, its giving an 404 error.

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almost all characters lose their special meanings inside a character class, including \ * and /

Try this: [a-zA-Z0-9_\/%*]+