If the "x" modifier is used, whitespace and comments in the regex are ignored.
re =
%r{
# year
(\d {4})
# separator is one or more non-digits
\D+
# month
(\d\d)
# separator is one or more non-digits
\D+
# day
(\d\d)
}x
p "the 1st date, 1984-08-08, was ignored".match(re).captures
--->["1984", "08", "08"]
