Fix bug in regular expression and make the regular expression more
strict.
In a string passed to new RegExp(), '[\t\s]' is identical to '[ts]' and
not `/[\t\s]/`. For that, the backslash needs to be escaped in the
string. Futhermore, `\t` is the tab character and is included in the
special regexp value `\s` so is unnecessary.
That would reduce the RegExp to new RegExp(`^${value}\\s*;?`) but
there's no point in matching 0 or more space characters followed by 0 or
one semi-colons as that will match no matter what follows `value`.
To make it more strict, require one of space, semicolon, or
end-of-string after value.
