John M. Dlugosz has asked for the wisdom of the Perl Monks concerning the following question:

How can I process "lazy" XML like our <code> tags? The best solution would work within the Twig framework, but here is a stand-alone preprocessor that does it.

This concept demo below will scan the proto-XML and escape out chars in the elements that are supposed to be literal.

I thought about using Parse::RecDecent, or other parsing technology, but it should be a simple problem. I'm wondering if this general idea, of using cascaded RE's with a continuing "pos", can be improved.

use strict; use warnings; sub is_literal ($$) { my ($name, $attrs)= @_; return ($name eq 'listing') || ($name eq 'signature'); # simple demo +. # change this to analyse $name and $attrs to decide whether to treat +this literally. } sub escape_out ($) { my $passage= shift; $passage =~ s/&/&amp;/g; $passage =~ s/</&lt;/g; return "[[[* $passage *]]]"; # [[[]]] to visibly show that the right + "bite" was taken. } sub scan ($) { my @passages; my $line= shift; # first pass: note what sections need treatment, without actually mod +ifying the string. # modifying the string would mess up the "pos" used by the RE's. while ($line =~ m/<\s*(\w+)([^>]*)>/g) { # for every start tag... my $startpos= pos($line); my $name= $1; if (is_literal ($name, $2)) { # if targeted, find the matching end tag using simple pattern ( +ignoring other stuff). # this skips that passage for the continued search of all start + tags. $line =~ m/<\/$name>/g; my $endpos= pos($line); unshift @passages, [$startpos, $endpos-(length($name)+3)]; } } # second pass: process the sections noted above, from right-to-left s +o # positions don't change. foreach my $range (@passages) { my ($start, $end)= @$range; my $length= $end-$start; substr($line, $start, $length)= escape_out (substr($line, $start, +$length)); # is there an easier way to do that without substr'ing twice? } print $line; } my $testdata= <<'EOF'; <method name="mainloop"> <signature virtual="1">int mainloop (ratwin::message::MSG&)</sig +nature> <P>This is the canonocal logic of the message pump. It looks ap +roximatly like this:</P> <listing> use & and <things> in here. MSG msg; while ( GetMessage(msg) ) { if (msg.hwnd == 0) thread_message (msg); else { if (!pre_translate (msg)) { // check IsDialog, Trans +lateAccelerator if (!translate_key_even(msg)) // Win32 TranslateMe +ssage DispatchMessage(msg); } } } return (msg.wParam); </listing> <P>Override this if you need to customize this beyond the point +provided for by the virtual functions provided for the individual steps.< +/P> </method> EOF scan ($testdata);