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

Hi Monks!
I am trying to call a small perl script that has a menu I am using across a bunch of pages in my site. The issue I am having is that when I use this test program:
#!/usr/bin/perl -w

use strict;
use CGI qw(:standard);
use URI::Escape;


require "call_b.pl";

my $go_menu = &menu;

#print "Content-type: text/html\n\n";

#print $go_menu;

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It gets an error like:
Can't use an undefined value as a SCALAR reference
The error is from the call_b.pl script:
#!/usr/bin/perl -w

use strict;
use CGI qw(:standard);
use URI::Escape;

my $address;

sub menu {

print qq|
    <td>
      <ul> 
        <li><a href="home.pl?contatc=${ uri_escape( $address ) }&amp;s
+elected_tab=a" target="_top">home<b></b></a></li> 
        <li><a href="home.pl?contatc=${ uri_escape( $address ) }&amp;s
+elected_tab=b" target="_top"><span></span>about<b></b></a></li> 
        <li><a href="home.pl?contatc=${ uri_escape( $address ) }&amp;s
+elected_tab=c" target="_top"><span></span>contact<b></b></a></li>    
+           
      </ul>
    </td>
|;

}
1;

[download]

Is this a glob error? What the best way to do this, if anyonw knows it would be nice!
Thanks for looking!

Replies are listed 'Best First'.
Re: SCALAR ref error help!
by delirium (Chaplain) on Aug 03, 2011 at 15:38 UTC

    There are a few bad things going on. First, change the name of the sub to something else; "menu" is used by one of the other modules, and there is a name collision.

    Second, $address doesn't get initialized anywhere. Third, don't print from the sub, return the value.

    Last, the uri_escape interpolation seems to be wrong somehow, but I didn't try to rewrite it as is, because it's hard to read, and you're doing it three times needlessly. Instead, call it outside of the qq statement. Try something like this:

    Main script: 
    #!/usr/bin/perl -w

use strict;
use CGI qw(:standard);
use URI::Escape;


require "call_b.pl";

my $go_menu = &menu2;
print "Content-type: text/html\n\n";
print $go_menu;

    [download]
    call_b.pl 
    #!/usr/bin/perl -w

use strict;
use CGI qw(:standard);
use URI::Escape;

my $address = uri_escape("some address");

sub menu2 {
return qq|
    <td>
      <ul>
        <li><a href="home.pl?contatc=$address&amp;selected_tab=a" targ
+et="_top">home<b></b></a></li>
        <li>etc..</li>
      </ul>
    </td>
|;

}
1;

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Re: SCALAR ref error help!
by ikegami (Patriarch) on Aug 03, 2011 at 18:11 UTC 
    "${foo}"

    [download]
    means 
    "$foo"

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    but anything more complex and $... / ${ ... } becomes a derefence operator. Solutions: 
    print qq|...contatc=|. uri_escape( $address ) .qq|...|;

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    printf qq|...contatc=%s...|, uri_escape( $address );

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    my $address_uri = uri_escape( $address );
print qq|...contatc=$address_uri...|;

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    print qq|...contatc=${\( uri_escape( $address ) )}...|;

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Re: SCALAR ref error help!
by Gulliver (Monk) on Aug 03, 2011 at 15:35 UTC

    The qq function does interpolation so ${ is seen as dereferencing something that isn't defined.

    You didn't mention the other warning "Subroutine menu redefined at call_b.pl line 9." I don't know anything about CGI or URI so not sure if that is an issue. But it looks like calling uri_escape is returning undef.

    Something else I noticed is that my $go_menu = &menu; will not assign anything to $go_menu since menu doesn't return anything.

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      What if I change the menu sub to: 
      sub menu {

$address = q|
    <td>
      <ul> 
        <li><a href="home.pl?contatc=${ uri_escape( $address ) }&amp;s
+elected_tab=a" target="_top">home<b></b></a></li> 
        <li><a href="home.pl?contatc=${ uri_escape( $address ) }&amp;s
+elected_tab=b" target="_top"><span></span>about<b></b></a></li> 
        <li><a href="home.pl?contatc=${ uri_escape( $address ) }&amp;s
+elected_tab=c" target="_top"><span></span>contact<b></b></a></li>    
+       
      </ul>
    </td>
|;
return;
}
Suggestions? Or would that be ok to have this line then: <code>my $go_
+menu = &menu;

      [download]

      Thanks! </code>
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Re: SCALAR ref error help!
by duyet (Friar) on Aug 04, 2011 at 06:44 UTC
[reply]

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