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

Monks,

I've encountered the following weirdness:

#!/usr/bin/perl
#use Switch;
print while <DATA>;
__DATA__
some
data
here

[download]

If I uncomment the "use Switch" line, it prints nothing. Bug, or am I missing something? perl v5.12.2.

Replies are listed 'Best First'.
Re: Switch and __DATA__
by Perlbotics (Archbishop) on Jun 16, 2011 at 13:16 UTC
[reply]
[d/l]

      Aha, so that's how you do it nowadays! Guess I don't use switch statements all too often. :) Thank you.

[reply]
Re: Switch and __DATA__
by MidLifeXis (Monsignor) on Jun 16, 2011 at 12:53 UTC

    Confirmed on the CB (thanks Corion) - this is a problem with a source filter. Switch does some funky things with the source (via regex, I believe), and sometimes it fails.

    --MidLifeXis

[reply]

      Thank you, I'll revert to a hand crafted switch construct then.

[reply]
Re: Switch and __DATA__
by Tux (Canon) on Jun 16, 2011 at 13:36 UTC

    Pne more (very good) reason to always use strict and warnings, as that would have clearly pointed you to who's fault it is:

    $ perl5.12.2 -we'use Switch'
Switch will be removed from the Perl core distribution in the next maj
+or release. Please install it from CPAN. It is being used at -e, line
+ 1.
$

    [download]

    Switch is from 2009, and it has been deprecated in 5.12 and has been removed from 5.14 and up:

    $ perl5.14.0 -we'use Switch'
Can't locate Switch.pm in @INC (@INC contains: /media/Tux/perls/lib/si
+te_perl/5.14.0/i686-linux-64int /media/Tux/perls/lib/site_perl/5.14.0
+ /media/Tux/perls/lib/5.14.0/i686-linux-64int /media/Tux/perls/lib/5.
+14.0 .) at -e line 1.
BEGIN failed--compilation aborted at -e line 1.
$

    [download]

    As already noted, don't use Switch. With recent perl versions, use given/when or for/when.

    FWIW Switch makes your whole script barf on unpredictable points when you are using defined-or // which is way more useful than Switch.


    Enjoy, Have FUN! H.Merijn
[reply]
[d/l]
[select]

      My original script has use warnings and strict, but perl does not produce any warnings with "use Switch". I'm on Windows (Active State Perl) atm, I might add.

[reply]

        I just tried with Strawberry, and it also does not issue a warning. It must be a Windows problem. I'll ping their maintainers.

        I hope my other information was useful for you though.


        Enjoy, Have FUN! H.Merijn
[reply]

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