替换所有换行符的实例，而不是标签。

<br />

[something][~something]

something

#!/usr/bin/perl
#

$in = \"foo\\nbar\\nbaz[something]else\\nis\\n[~something]\\nHappening\\n[something]else\\nis\\n[~something]here\\n\";
$out = \"\";

while ($in =~ s/^(.*?)(\\[something\\].*?\\[~something\\])//s)
{
  my($before,$during) = ($1,$2);
  $before =~ s/\\n/<br \\/>/g;
  $out .= $before.$during;
}
$in =~ s/\\n/<br \\/>/g;
$out .= $in;
print $out;