Looking at the Camel book, 3rd edn., table 5-1 on page 150, the entry for /s
says "Let . match newline ... " which sort of implies that /m
doesn't. So it is the treatment of the "." metacharacter that changes between the two. This with no modifying flag also matches
($span_d) = $str =~ /(\d\d\w+\s\w+\d\d/;
This might imply that the default behaviour of m/.../ with no modifying flag is the same as m/.../m. I will delve into the documentation when I get a chance.
This passage is in the "perlre" manual page
m Treat string as multiple lines. That is, change "^" and
"$" from matching the start or end of the string to
matching the start or end of any line anywhere within
s Treat string as single line. That is, change "." to
match any character whatsoever, even a newline, which
normally it would not match.
The "/s" and "/m" modifiers both override the $*
setting. That is, no matter what $* contains, "/s"
without "/m" will force "^" to match only at the
beginning of the string and "$" to match only at the end
(or just before a newline at the end) of the string.
Together, as /ms, they let the "." match any character
whatsoever, while still allowing "^" and "$" to match,
respectively, just after and just before newlines within
perl v5.8.4 Last change: 2004-01-17 1
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