I'm using the regexp function call in my LUA script and trying to come to grips with the rules/syntax supported by this function. Based on experiments, an expression delimited by slashes, / ... /, is treated as a posix regular expression. However, when no slashes are present, the rules/syntax becomes a bit foggy. It appears to be some sort of combination of glob-style pattern matching mixed with a tiny subset of posix regex.
Does any documentation exist to clearly define the expressions supported by this function?