Hi Rob,
Rob Dixon wrote on 29.04.2004:
>Jan Eden wrote:
>>The obvious problem is, that the variables are not interpolated
>>according to their current value in the scripts, i.e. although
>>
>>$mother_id = 453; and $title = "Title";
>>
>>The $page_head variable will an contain empty title tag and
>>show_local.pl parameter after the do command.
>
>Hi Jan.
>
>I felt like a quick Perl 'fix' :)
>
Reminds me of our last do/eval discussion. I seem to never learn it. I never seem to
learn it. ;-) While we're talking about scope.
>perldoc -f do says:
>
>[do] also differs in that code evaluated with "do FILENAME" cannot
>see lexicals in the enclosing scope; "eval STRING" does.
>
Ok, but $mother_id and $title are not lexicals within the html code. Or are they? Or,
wait... the enclosing scope refers to the scope enclosing the expression evaluated? So
it's the outer $mother_id and $title which cannot be seen.
>so you need to eval the contents of a file. If in page_head.pl you
>write this:
>
>q{ qq{ <?xml version="1.0" encoding="utf-8"?> <!DOCTYPE html PUBLIC
>"-//W3C//DTD XHTML 1.0 Transitional//EN"
>"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd";> <html
>xmlns="http://www.w3.org/1999/xhtml"; xml:lang="de" lang="de"> <head>
><title> $title </title> </head> <body> <a
>href="show_local.pl?id=$mother_id" class="head" target="_self">UP</a>
><div class="textbox"> <!-- begin content --> </body> </html>
>}};
>
>then I hope you can see that
>
>do 'page_head.pl'
>
>returns the string without the enclosing q{ .. }. i.e. the
>double-quoted string that you want to eval. So you can then write
>
>use strict; use warnings;
>
>my $title = 'Title'; my $mother_id = '453';
>
>print eval do 'page_head.pl';
>
Dang. do AND eval. That's looks terribly smart to me, although someone less dim witted
than myself would have seen this himself. Or herself, for that matter.
Thanks a lot, Rob. You are one of the most helpful people around.
- Jan
--
A common mistake that people make when trying to design something completely foolproof
is to underestimate the ingenuity of complete fools.
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