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

There is something I'm not understanding about the search engine. With the code and data below I get the first substitution made but not the second, i.e., the </INSERT-TOPIC> is not substituted for </TOPIC>. When I print out the match it matches "<CASE-STUDY(^>*)>". I thought the search engine started over at the beginning of the string and that the second match should be <CASE-STUDY.*?<\/CASE-STUDY><\/INSERT-TOPIC>. So I'm not misunderstood, of course I don't expect it to match the literal ".*?" and so forth but its equivalent data. Hope this makes sense. 
if ($tmp_buffer =~ /^<CASE-STUDY/i) {        
   $tmp_buffer =~ /<CASE-STUDY[^>]*><TOPIC-INFO><TITLE>([^<]*)<\/TITLE
+>/i;
   my($xtitle) = $1;
   $tmp_buffer =~ s/<CASE-STUDY([^>]*)>/<TOPIC ID="" HEADING-LEVEL="1"
+><TOPIC-INFO><TITLE>$xtitle<\/TITLE><\/TOPIC-INFO><CASE-STUDY$1>/i;
   $tmp_buffer =~ s/(<CASE-STUDY.*?<\/CASE-STUDY>)<\/INSERT-TOPIC>/$1<
+\/TOPIC>/si;
   print "debug - $&\n";
}

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<INSERT-TOPIC>
<CASE-STUDY ID="1"><TOPIC-INFO><TITLE>Case Study</TITLE></TOPIC-INFO>
<PARA>poop</PARA>
</CASE-STUDY>
</INSERT-TOPIC>

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Re: Why doesn't the search engine start from scratch
by ikegami (Patriarch) on Jan 27, 2012 at 23:39 UTC
    • $tmp_buffer =~ /^<CASE-STUDY/ doesn't match. /m is needed to make "^" match at the start of a line.
    • The last regex pattern doesn't match because </CASE-STUDY></INSERT-TOPIC> doesn't exist in the input. There's a newline between the two tags.
    • You don't include the last substitution in your last print. 
    if ($tmp_buffer =~ /^<CASE-STUDY/mi) {
                                 ^
                                 |

   $tmp_buffer =~ /<CASE-STUDY[^>]*><TOPIC-INFO><TITLE>([^<]*)<\/TITLE
+>/i;
   my($xtitle) = $1;
   $tmp_buffer =~ s/<CASE-STUDY([^>]*)>/<TOPIC ID="" HEADING-LEVEL="1"
+><TOPIC-INFO><TITLE>$xtitle<\/TITLE><\/TOPIC-INFO><CASE-STUDY$1>/i;
   $tmp_buffer =~ s/(<CASE-STUDY.*?<\/CASE-STUDY>)\s*<\/INSERT-TOPIC>/
+$1<\/TOPIC>/si;
                                                  ^^^
                                                  |||
   print "debug - $tmp_buffer\n";
                  ^^^^^^^^^^^
                  |||||||||||
}

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