As moritz suggested. Anyway if you want to use regex and just want to see $1 and $3 try to make the optional part capturing since you don't care about $2. Something like this:

my $regex = '<div id="aaaa">([.\w\s]*?)(<ul id="ccc">[.\s\w]*?</ul>)?(
+[.\s\w]*?)</div>';
[download]

This is the output if that's what you seek:

Text 1 found 
    text tex text

    more text
Text 2 found 
    text text text

    more text
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Regards