Pattern matching lines starting with double comment characters

[goncholden]

I want to match lines that start with double comment characters in source code 
files.

I am currently using

pn_ere = "^[[:space:]]*([#;!]+|@c|//)[[:space:]]+"​

The pattern handles possible spaces at the beginning and end of lines.

But the pattern does not specify double comment characters

Case of ##
Case of ;;
Case of !!

How can adapt the pattern for these cases?