Permanent <<use feature ":5.10";>>

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

I have learnt that in order to use featrures like the statement "say" or the "switch" style programming structure, I have to initiate all my Perl programs with the following declaration:

use feature ":5.10";
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Is there some sort of instructing Perl to take that as a default. I mean, if I want, for instance, to use those features from the command line, say, to use

$ ls -l | perl -ane 'say "@F[5..7]"'
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instead of the more verbose

$ ls -l | perl -ane 'print "@F[5..7]\n"'
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Do you have any comments on this?
Thanks!
--Sergio.

Comment on Permanent <<use feature ":5.10";>> Select or Download Code

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Re: Permanent <<use feature ":5.10";>> by mirod (Canon) on Mar 08, 2012 at 18:01 UTC
Use `-E` instead of `-e`: `ls -l \| perl -anE 'say "@F[5..7]"'` From `man perlrun`: -E commandline behaves just like -e, except that it implicitly enables all optional features (in the main compilation unit). See feature.	[reply] [d/l]
Re: Permanent <<use feature ":5.10";>> by toolic (Bishop) on Mar 08, 2012 at 18:28 UTC
Another possibility is to set the PERL5OPT environment variable: `$ setenv PERL5OPT -Mfeature=:5.10 $ perl -e 'say 5' 5` [download]	[reply] [d/l]
Re: Permanent <<use feature ":5.10";>> by JavaFan (Canon) on Mar 08, 2012 at 18:03 UTC
For command line perl, just replace `-e` with `-E`. For programs, just start your programs with `use 5.010;` (or some higher number). Declaring a minimum version is a good idea anyway. If you find that too much typing, spend a few minutes learning how to add a macro in your editor.	[reply] [d/l] [select]
Re: Permanent <<use feature ":5.10";>> by CountZero (Bishop) on Mar 08, 2012 at 19:46 UTC
I do a `use Modern::Perl` at the start of my programs. That gets me all the new features, strictures and warnings as well and 'C3' method resolution order. CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James My blog: Imperial Deltronics	[reply] [d/l]
Re: Permanent <<use feature ":5.10";>> by kcott (Archbishop) on Mar 08, 2012 at 19:58 UTC
Using Modern::Perl from the commandline is probably just as much typing but, as it provides quite a few other items (strict, warnings, etc.), you might find it's worth it. Simply to get access to `say()`, I'd just use `-E` as mirod suggested (above). -- Ken	[reply] [d/l] [select]
Re: Permanent <<use feature ":5.10";>> by LanX (Saint) on Mar 08, 2012 at 17:55 UTC
IIRC you can define a rc-file with perl-code which is sourced by each instance... ... to be continued... Cheers Rolf UPDATE: see Re^3: Permanent <<use feature ":5.10";>>	[reply]
Re^2: Permanent <<use feature ":5.10";>> by juliosergio (Sexton) on Mar 08, 2012 at 17:59 UTC
Ok, but what should be the name of the rc-file and where is to be located?	[reply]
Re^3: Permanent <<use feature ":5.10";>> by LanX (Saint) on Mar 08, 2012 at 20:07 UTC
Finally I found what I had in mind, see `$Config{sitelib}/sitecustomize.pl` in perlrun But contrary to toolic's PERL5OPT it's site-wide, so better think twice about what could be affected. Cheers Rolf	[reply] [d/l]
Re^3: Permanent <<use feature ":5.10";>> by LanX (Saint) on Mar 08, 2012 at 18:06 UTC
I said IIRC and your too fast! :) Couldn't find it seems I was confusing with the debugger or perl6 feature. Sorry! Anyway for the general problem it should be possible to alias perl to a command which loads a module first which does whatever settings you want. For your special problem the mentioned -E is good enough. Cheers Rolf	[reply]
Re: Permanent <<use feature ":5.10";>> by ForgotPasswordAgain (Priest) on Mar 09, 2012 at 00:22 UTC
Probably won't be a popular comment, but you asked for any comments. Mine: don't use 'say' (or 'switch'). There, I sayed it. (How to justify it... Time saved? You spent some amount of time puzzling over it, then posted to perlmonks asking how to do it. A lot of time there. Or maybe it's clearer? 'say', a new feature, works now because....somehow it's been enabled. Well, if you set some environment variable or whatever, which won't work elsewhere. Seems not really so clear. Easier to wait a few years before using new syntax of dubious value, IMHO. Just because UNIVERSAL::can($you, 'do_something') doesn't mean UNIVERSAL::should($you, 'do_something') :))	[reply]
Re^2: Permanent <<use feature ":5.10";>> by mirod (Canon) on Mar 09, 2012 at 06:51 UTC
Although I don't agree with you, 5.10 has been out for long enough to be pretty much everywhere, in this case it's fairly easy to emulate `say` using `-l`: `ls -l \| perl -l -ane 'print "@F5..7"'`	[reply]

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