$s = '
<p>something something</p>
<h2>blah blah blah</h2>
<p>something something</p>
';

$before = '<h2>([^<]+)</h2>';
$after = '"<h1>$1</h1>"';

$s =~ s/$before/$after/ee;

print $s;
[download]

<p>something something</p>
<h1>blah blah blah</h1>
<p>something something</p>

Tool completed successfully
[download]

Picture me slapping my forehead. Thank you so much.

I'd forgotten all about "ee" but now I'm remembering Merlyn's classic /old macdonald/eieio regex.

---




($_='kkvvttuubbooppuuiiffssqqffssmmiibbddllffss')
 =~y~b-v~a-z~s;                             print
[download]

I can easily break this code by feeding it a valid html string:

$s = '
<p>something something</p>
<h2>blah <<< blah blah</h2>
<p>something something</p>
';
[download]

Update:

BUU, although parsing is not the purpose, you have to realize that implicitly it is done any way. Regexp is obviously a kind of parsing, and it has been repeatedly mentioned by many monks here that, regexp is not a good way to deal with html.

It is not an easy task to come up with perfect regexp for dealing with html.

On the other hand, although the purpose is not parsing, parsing is still a valid tool, isn't it? In this case, actually a better tool.

But he's not parsing html. The parent node never even mentioned parsing html. All he wants to do is match a certain substring and replace it with another one. The minor fact that this string happens to contain data that superficially resembles html has absolutely no bearing on this.

use HTML::Parser;
use strict;

my $str = '<p>something something</p>
<h2>blah <<< blah blah</h2>
<p>something something</p>';

my $parser = HTML::Parser->new(default_h=> [\&handler, "tagname, text"
+]);
$parser->parse($str);

sub handler {
    my ($tag, $text) = @_;
    if ($tag) {
        if ($tag eq "h2") {
             print "<h1>";
        } else {
             print "<$tag>";
        }
    } else {
        print $text;
    }
}
[download]

I can easily break this code by feeding it:

my $str = '<p>something something</p>
<h2>blah </a> blah blah</h2>
<p>something something</p>';
[download]


Output:

<p>something something<p>
<h1>blah <a> blah blah<h1>
<p>something something<p>
[download]

(Whered the slash before the a go? Heck if I know)

Thanks for the code. It really was just an example though. I was thinking about the Big Picture rather than the code at hand.

---




($_='kkvvttuubbooppuuiiffssqqffssmmiibbddllffss')
 =~y~b-v~a-z~s;                             print
[download]

use strict;

my $s = '<p>something something</p>
<h2>blah </a> blah blah </h2>
<p>something something</p>';

my $start = '<h2>';
my $end = '</h2>';

my $first = index($s,$start);
my $last = index($s,$end,$first);

substr($s, $first, $last-$first+length $end) = '<h1>'.substr($s,$first
++length $start,$last-$first-length $start).'</h1>';

print $s;
[download]

while(1)
{
    if( index( substr( $s, $start_pos, $end_pos-$start_pos ), $start_t
+ag ) != -1 )
    {
        $end_pos = index( $s, $end_tag, ++$end_pos );
    }
    else
    {
        last; # $end_pos is good
    }
}
[download]

s/<h2>/<h1>/gi;
s#</h2>#</h1>#gi;
[download]

You could also use a stylesheet to change the properties of H2 tags and not bother replacing any existing markup.