dw_dev_training: Nifty perl trick I learned about today

pauamma (

pauamma) wrote in

dw_dev_training,
@ 2010-08-31 06:34 pm UTC

Entry tags:

perl, tips

Nifty perl trick I learned about today

Context was someone asking why

print "Hello, world!\n" && die;

doesn't output anything. Someone replied with a nifty trick to help figure this out:

perl -MO=Deparse -e 'print "Hello, world!\n" && die;'

(go ahead and try it in your Dreamhack).

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sophie
2010-08-31 11:38 pm UTC (link)

Also, if you need to do this trick but don't know what the operator precedence is, you can add ",-p" after the "Deparse" in order to get Perl to print parentheses to show exactly how things get calculated.

One thing, btw - this won't work as a built-in code beautifier because you'll find that some string literals aren't kept; they're transformed to '???'. That's because it's a constant value that Perl optimised away for whatever reason. (The perldoc for B::Deparse explains more.)

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	no subject pne 2010-09-01 06:18 am UTC (link)
	B::Deparse is really fun. Have you thought about cross-posting this to command_liners? (Reply to this) (Thread) (Hide 1 comment) (Show 1 comment)

	no subject pauamma 2010-09-01 02:40 pm UTC (link)
	http://command-liners.dreamwidth.org/4982.html (Reply to this) (Thread from start) (Parent)

	no subject afuna 2010-09-01 10:27 am UTC (link)
	Oh neat. (What is the O for? I can find -M in `man perlrun`, but I can't find -O) (Reply to this) (Thread) (Hide 2 comments) (Show 2 comments)

	no subject alierak 2010-09-01 01:28 pm UTC (link)
	It's the argument to -M. "perldoc O" should do something. (Reply to this) (Thread from start) (Parent) (Thread) (Hide 1 comment) (Show 1 comment)

	no subject afuna 2010-09-02 05:45 am UTC (link)
	Oh dur. So obvious now, thanks! (Reply to this) (Thread from start) (Parent)

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