use of << on comand line

cweeble has asked for the wisdom of the Perl Monks concerning the following question:

Hello monks. I am trying to read the input from a multi-line command.

i.e. Given the following command:-

$./myscript.pl data_item1 data_item2 <<QQ<br>
hello<br>
world<br>
QQ
[download]

I can read the two data_items physically specified on the command line by reading elements of @ARGV, but how does one read in those two additional lines of data ? I am trying to do this with perl 5.8.8

Comment on use of << on comand line Download Code

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Re: use of << on comand line by hippo (Archbishop) on Jun 04, 2018 at 14:18 UTC
Try: `my @shellheredoc = <STDIN>;` [download] PS. Don't forget to chomp if required.	[reply] [d/l]
Re^2: use of << on comand line by ikegami (Patriarch) on Jun 04, 2018 at 19:45 UTC
Or shift out the contents of `@ARGV` and use `<>`. This is a far more flexible and standard approach.	[reply] [d/l] [select]
Re^2: use of << on comand line by cweeble (Novice) on Jun 04, 2018 at 14:45 UTC
Thanks. That worked. :)	[reply]
Re: use of << on comand line by Eily (Monsignor) on Jun 04, 2018 at 14:18 UTC
That's the Heredoc syntax (as interpreted by your shell in thiscase, not perl). It simply writes the data to the standard input so you can read it with `<STDIN>` (the magical `<>` will try to use the parameters as the name of files to read from, unless you shift from @ARGV).	[reply] [d/l] [select]
Re^2: use of << on comand line by cweeble (Novice) on Jun 04, 2018 at 14:51 UTC
Thanks Eily. It works now :) I'll have to remember to watch out for that magical <> feature you mentioned. I never realised it works like that... Fortunately I usually shift parameters from @ARGV.	[reply]
Re^3: use of << on comand line by Eily (Monsignor) on Jun 04, 2018 at 15:04 UTC
You can find the documentation for the feature in perlop (search for "The null filehandle"). And you'll find more info on the problems of the magical `<>` and a safer version here	[reply] [d/l]