#!/usr/bin/perl -T

use strict;
use warnings;
use CGI::Carp qw(fatalsToBrowser);

print "Content-type: text; charset=utf-8\n\n";

my $teststring = qq|[pic w=100px h=50px style=test] some text
[infobox headline=Hello world! content=[pic w=50 h=50 style=left]
hier ist mein text.] [gallery path=[host]myfolder/ style=cool navi=standard] [host]|;

print "<h2>input</h2>\n$teststring";
print "<h2>output</h2>\n";
print &GetTags ($teststring);

sub GetKeyValue {
my ($tag, $attr) = @_;
my %KeyVal = $attr =~ m[(\S+)\s*=\s*(\S+)]g;
my $testkeyval = "";
my $totalkey = keys %KeyVal;
my $count= 0;
my $whitespace = " ";

for my $key (sort keys %KeyVal) {
if ($totalkey == $count) {$whitespace = ""};
$testkeyval .= "$key=\"$KeyVal{$key}\"$whitespace";
$count++;
}

if ($tag eq "pic") { return "{pic $testkeyval /}"; }
if ($tag eq "gallery") { return "{gallery $testkeyval /}"; }
if ($tag eq "infobox") { return "{infbox $testkeyval /}"; }
if ($tag eq "host") { return "http://www.example.com/"; }

}


sub GetTags {
    my ($text) = @_;
    my $output = "";
    my $stack = [];
    while (length $text) {
        if (($text =~ s/^\[(pic|gallery|infobox)\s//si) # tag mit attr
                || ($text =~ s/^\[(host)//si)) # tag ohne attr
                {
            my $name = $1;
            # tag
            my $attr = "";
            if ($text =~ s/^([^\[\]]+)//) {
                $attr = $1;
            }
            push @$stack, [$name, $attr];
        }

        else {
            my $out;
            if ($text =~ s/^\[//) {
                $out = "[";
            }
            if ($text =~ s/^\]//) {
                # closing tag
                                if (@$stack) {
                my $last = pop @$stack;
                my ($name, $attr) = @$last;
                $out = &GetKeyValue($name, $attr);
                                }
            }
            else {
                # text
                if ($text =~ s/^([^\[\]]+)//) {
                    $out = $1;
                }
            }
            if (@$stack > 0) {
                $stack->[-1]->[2] .= $out;
            }
            else {
                $output .= $out;
            }
        }
    }
    return $output;

}

<h2>input</h2>
[pic w=100px h=50px style=test] some text
[infobox headline=Hello world! content=[pic w=50 h=50 style=left]
hier ist mein text.] [gallery path=[host]myfolder/ style=cool navi=standard] [host]<h2>output</h2>
{pic h="50px" style="test" w="100px"  /} some text
{infbox headline="Hello"  /} {gallery  /} http://www.example.com/