Couldn't parse first regexsecond regexeither regex
Equivalent
Accepted by first but not second:

        
Accepted by second but not first:

        

Syntax
a | b
union
a b
concatenation
a?
option
a*
repetition (zero or more)
a+
repetition (at least one)
a^N
repetition (exact count)
(a)
atom
[space]
ignored
(in order of increasing precedence)