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

Greetings monks!
I've been really looking at chromatic's Modern::Perl today. I'm finding that I'm even less a Perl hack, than I thought I was. To the point; I was working on a fairly simple script, when I came across M::P. So I added it to the use list. Well, that threw a bunch of new errors to the list I was already attempting to resolve. So, I figured I'd start small/simple. So I wrote the following as a starting template: 
#!/usr/bin/perl -Tw
# a stupid simple script that prints a form && echoes any input

use CGI;
use Modern::Perl 2011;

my $head ='<!DOCTYPE html><head></head><body>
<br />
<form method="post" action="/valid-form.cgi">
';
my $form ='    <label for="input">Input: </label><input type="text" na
+me="input" value="" />
    <input type="submit" value="Post Input" />
';
my $foot ='
</form></body></html>';
print "content-type:text/html; charset=utf-8\n\n";
print $head;
print $form;
my $query = CGI->new;
$input = $query->param('input');
if (!$input) {
    print "<br />No input";
}else{
    print "<br />$input";
}    
print $foot;

[download]
Simple enough --eh? NO. Seems that in the absence of M::P, everything is just Ducky. But now, with the addition of M::P, it fails. 
Global symbol "$input" requires explicit package name at
Global symbol "$input" requires explicit package name at
Global symbol "$input" requires explicit package name at

[download]
Hmm... the $input stuff is a near Copy->Paste from the CGI pod.
I'm stumped.
Anyone care to comment?

Thank you for all your time, and consideration.

--Chris

#!/usr/bin/perl -Tw
use perl::always;
my $perl_version = (5.12.5);
print $perl_version;

Replies are listed 'Best First'.
Re: Why does Modern::Perl hate CGI.pm || my simple form?
by choroba (Cardinal) on Nov 05, 2013 at 23:20 UTC
    Modern::Perl means strict. Under strict, every variable must be declared. $input is not declared. See also my.

    Update: Try also diagnostics or splain: 

    $ echo 'Global symbol "$input" requires explicit package name at -e li
+ne 1.' | splain
Global symbol "$input" requires explicit package name at -e line 1 (#1
+)
    (F) You've said "use strict" or "use strict vars", which indicates
+ 
    that all variables must either be lexically scoped (using "my" or 
+"state"), 
    declared beforehand using "our", or explicitly qualified to say 
    which package the global variable is in (using "::").

    [download]
    لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
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[select]
      Greetings, and thank you for taking the time to respond.
      Good advise -- I'll take it!

      Thanks again.

      --Chris

      #!/usr/bin/perl -Tw
use perl::always;
my $perl_version = (5.12.5);
print $perl_version;
[reply]
Re: Why does Modern::Perl hate CGI.pm || my simple form?
by LanX (Saint) on Nov 05, 2013 at 23:21 UTC
[reply]
      "BTW: CGI.pm must die!"
      LOL!
      I'm inclined to agree. I find the only time I use it, it to keep the code/script looking clean/tidy.
      Using it otherwise I think would just make me lazy/uninformed.
      Thanks for the informative response, Rolf!
      #!/usr/bin/perl -Tw
use perl::always;
my $perl_version = (5.12.5);
print $perl_version;
[reply]
        In case the solution was not obvious to other onlookers. Here's the corrected version that I should have known to do in the first place. :/ 
        #!/usr/bin/perl -Tw
# dead simple stupid script that echoes input
use CGI;
use Modern::Perl 2011;

my $head ='<!DOCTYPE html><head></head><body>
<br />
<form method="post" action="/valid-form.cgi">
';
my $form ='    <label for="input">Input: </label><input type="text" na
+me="input" value="" />
    <input type="submit" value="Post Input" />
';
my $foot ='
</form></body></html>';
print "content-type:text/html; charset=utf-8\n\n";
print $head;
print $form;
my $query = CGI->new;
my $input = $query->param('input');
if (!$input) {
    print "<br />No input";
}else{
    print "<br />$input";
}    
print $foot;

        [download]
        Take note of the additional my

        Best wishes.

        --Chris out...

        #!/usr/bin/perl -Tw
use perl::always;
my $perl_version = (5.12.5);
print $perl_version;
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Re: Why does Modern::Perl hate CGI.pm || my simple form?
by ww (Archbishop) on Nov 06, 2013 at 03:12 UTC
[reply]
[d/l]
      Greetings ww!
      Indeed. I did. As noted in the thread you mentioned; I updated to the current version of M::P. So things are (should) go as expected. :)

      Best wishes.

      --Chris out...

      #!/usr/bin/perl -Tw
use perl::always;
my $perl_version = (5.12.5);
print $perl_version;
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