Digit \d matching in regex

Q: matches (regex ("([[:blank:]]|^)[[:alnum:]_]*([[:blank:]]|$)")) of "one two three"
A: one
A: two
A: three
T: 458903

Q: operating system
A: AIX 7.1
T: 156964

Q: version of client
A: 9.2.0.360
T: 2123903