While I think I understand the Perl code, it does not find anything (as opposed to the original version of the hint).
Though I cannot find the -n and -e flags in man perl, I assume the command simply calls Perl with the supplied file as the default input argument and executes the actual Perl code. I guess the while condition is some fancy regular expressions code that simply chops up the dictionary file into individual words, stores each word in $a and compares $a with $text and prints it if it finds a match.
However, I think somewhere the reading of library file does not work, as the following simplified code should just read the file 'Untitled.txt' and print its contents:
perl -n -e 'while(/"]+"[^>"]+"[^>"]+"([^>"]+)"/g) { print $1,"n"; }' ~/Desktop/Untitled.txt

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I should mention that this works for 10.4. I haven't upgraded yet, just about backed up and ready to go. So the 10.5 dictionary may be in a different place and may be a different format.

The command switches are documented in "man perlrun".

-n makes perl read the input file in a while loop until the file is read completely.

-e indicates the next argument is a script.

The regex looks for a pattern like

<o:ent ..."...."..."..."...."> 

which indicates an entry in the dictionary. The actual entry word is between the last 2 double quotes which is caught by the brackets and referenced by the $1 in the while loop. The /g modifier at the end of the regex allows the while loop to loop through the file. The $a is needed to retain the "word" through another regex. The backslash-b's makes the regex the equivalent of -w.

Is that clear? Perl is a strange language.

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The dictionary indeed has a slightly different name in 10.5 but I corrected that already.
I had checked 'man perl' not 'man perlrun', thanks for pointing me to that.

Perl is still ok, regular expressions are what often throws me off.

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