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

Hello Monks,

I believe my problem is a general problem. I did a search, but found no answers.

Description:

There is a HTML file to be processed. I want to substitute a pattern with another one. There are many patterns to be processed, but I do not know how many. I came up a structure so that I can easily add a new pattern.

The structure looks like: 

$file= '<A NAME="TOC124" HREF="cvs.html#SEC124">A.8 commit--Check file
+s into the repository</A>';

 $c->{Anchor}{from}='<A NAME="(.*?)" HREF=".*?\#(.*?)">(.*?)</A>';
 $c->{Anchor}{to}='$3 |$2| *$1*';

foreach $item (keys %$c) {
    $from=$c->{$item}{from};
    $to=$c->{$item}{to};
    $file=~s/$from/$to/sg;
}

print "$file\n";

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There is hash reference $c where I plan to add more pattern as long as necessary. The main body foreach process each of the patterns.

The expected result is:
A.8 commit--Check files into the repository |SEC124| *TOC124*

The result of my program is:
$3 |$2| *$1*

Here the problem is that $1,$2 and $3 is not evaluated. This is reasonable as I coded like this. My question is how can I make them evaluated ?

Thanks for any of your suggestions!

Replies are listed 'Best First'.
Danger Will Robinson! False Laziness!
by skyknight (Hermit) on Jul 30, 2003 at 17:13 UTC

    Get a real templating engine. You're reinventing the wheel, and you're almost certain to reinvent a worse one, as this is actually a very messy problem. Do yourself a favor and look up something like Embperl or Mason.

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Re: how to evaluate a variable in a string?
by fglock (Vicar) on Jul 30, 2003 at 17:23 UTC

    This works, but it is certainly not the best way to do it:

    $file= '<A NAME="TOC124" HREF="cvs.html#SEC124">A.8 commit--Check file
+s into the repository</A>';

 $c->{Anchor}{from}='<A NAME="(.*?)" HREF=".*?\#(.*?)">(.*?)</A>';
 $c->{Anchor}{to}='$3 |$2| *$1*';

foreach $item (keys %$c) {
    $from=$c->{$item}{from};
    $to=$c->{$item}{to};
    eval "\$file=~s/\$from/$to/sg";
}

print "$file\n";
# A.8 commit--Check files into the repository |SEC124| *TOC124*

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Re: how to evaluate a variable in a string?
by sauoq (Abbot) on Jul 30, 2003 at 17:34 UTC
    My question is how can I make them evaluated ?

    The problem is this line of code:

    $c->{Anchor}{to}='$3 |$2| *$1*';
    Use double quotes to get variable interpolation: 
    $c->{Anchor}{to} = "$3 |$2|*$1*";

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    My mistake. I didn't fully understand the question.

    -sauoq
"My two cents aren't worth a dime.";
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Re: how to evaluate a variable in a string?
by chunlou (Curate) on Jul 30, 2003 at 22:01 UTC
    Similar to fglock's first answer except for the variation: 
    $file=~s/$from/eval'"'.$to.'"'/sge;

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Re: how to evaluate a variable in a string?
by Kageneko (Scribe) on Jul 30, 2003 at 18:28 UTC
    In the line you are doing the assignment: 
    $c->{Anchor}{to}='$3 |$2| *$1*';

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    You are using single quotes. If you use double quotes: 
    $c->{Anchor}{to}="$3 |$2| *$1*";

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    then it should be properly interpolated. Barring that, you can also use eval (as noted above) to interpolate the string.
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Re: how to evaluate a variable in a string?
by fglock (Vicar) on Jul 30, 2003 at 20:19 UTC

    Yet another way to do it. This is not exactly what you asked, but it may help (tested):

    $file= '<A NAME="TOC124" HREF="cvs.html#SEC124">A.8 commit--Check file
+s into the repository</A>';

 $c->{Anchor}{replace}= sub {
    $_[0] =~ s{<A NAME="(.*?)" HREF=".*?\#(.*?)">(.*?)</A>}
              {$3 |$2| *$1*}
 };

foreach $item (keys %$c) {
    $c->{$item}{replace}( $file );
}

print "$file\n";

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