...as 1 line.
How about 44? :-) This uses a parser to get the data you need and a template to put it all back together again.

Over the top? Possibly. I have a particular aversion to having any HTML in my code, even more so in a regex. It almost always ends in tears. This way I have no HTML in the code at all (the source and the template would normally be in separate files). YMMV. 

#!/usr/local/bin/perl

use strict;
use warnings;

use HTML::TokeParser::Simple;
use HTML::Template;

my $p = HTML::TokeParser::Simple->new(\get_html());
my ($in_pre, $pre);
while (my $t = $p->get_token){
    $in_pre++, next if $t->is_start_tag(q{pre});
    next unless $in_pre;
    last if $t->is_end_tag(q{pre});
    $pre .= $t->as_is;
}
my @lines = grep{/\S/} split /\n/, $pre;

my $tmpl = HTML::Template->new(scalarref => \get_tmpl());
my @loop = map{{line => $_}} @lines;
$tmpl->param(loop => \@loop);
print $tmpl->output;

sub get_html{
    return <<HTML;
<html>
<pre>
line 1
line 2
line 3
</pre>
</html>
HTML
}

sub get_tmpl{
    return <<TMPL
<html>
<TMPL_LOOP loop>
<p><TMPL_VAR line></p>
</TMPL_LOOP>
</html>
TMPL
}

[download]
<html>

<p>line 1</p>

<p>line 2</p>

<p>line 3</p>

</html>

[download]

In reply to Re: Substitution inside tags, as 1 line by wfsp
in thread Substitution inside tags, as 1 line by tel2

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
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