Q:\>perl -MYAPE::Regex::Explain -we "print for YAPE::Regex::Explain->new(shift)->explain;" "\s\r\n\t"
The regular expression:

(?-imsx:\s\r\n\t)

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  \s                       whitespace (\n, \r, \t, \f, and " ")
----------------------------------------------------------------------
  \r                       '\r' (carriage return)
----------------------------------------------------------------------
  \n                       '\n' (newline)
----------------------------------------------------------------------
  \t                       '\t' (tab)
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------