Here's a rough summary of TheDamian's reasoning:

/x (PBP pgs 236-237)

RegEx's are really programs and thus should follow the other guidelines presented in the book (the most obvious being to comment them).

/m (PBP pgs 237-239)

Perl should behave the way most people think it will behave. And thanks to common line-based UNIX utilities like sed, grep, and awk the default Perl behavior for ^ and $ will not behave as expected (by most people). So use /m to align expectations.

/s (PBP pgs 240-241)

Pretty much the same argument as used in /m -- Perl should behave the way people think it will behave.

In reply to Re: Best practice or cargo cult? by Argel
in thread Best practice or cargo cult? by robinbowes

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