in reply to Re^4: Reading Reg Exp
in thread Reading Reg Exp

According to the perlrecharclass manpage:

\s matches any single character that is considered whitespace. In the ASCII range, \s matches the horizontal tab (\t), the new line (\n), the form feed (\f), the carriage return (\r), and the space.

It also says:

Without a locale or EBCDIC code page, \s matches the five characters mentioned in the beginning of this paragraph.

Update: Link fixed.