Perl syntax errors on declaring a large constant array - perl

Question

I want to declare a huge list of constant array like:
my #tlds = (ac ad ae aero af ag ai al am an ao aq ar arpa as asia at au aw ax az ba bb bd be bf bg bh bi biz bj bm bn bo br bs bt bv bw by bz ca cat cc cd cf cg ch ci ck cl cm cns
co com coop cr cu cv cw cx cy cz de dj dk dm do dz ec edu ee eg er es et eu fi fj fk fm fo fr ga gb gd ge gf gg gh gi gl gm gn gov gp gq gr gs gt gu gw gy hk hm hn hr ht hu id ie
il im in info int io iq ir is it je jm jo jobs jp ke kg kh ki km kn kp kr kw ky kz la lb lc li lk lr ls lt lu lv ly ma mc md me mg mh mil mk ml mm mn mo mobi mp mq mr ms mt mu museum mv mw mx my mz na name nc ne net nf ng ni nl no np nr nu nz om org pa pe pf pg ph pk pl pm pn pr pro ps pt pw py qa re ro rs ru rw sa sb sc sd se sg sh si sj sk sl sm sn so sr st su sv sx sy sz tc td tel tf tg th tj tk tl tm tn to tp tr travel tt tv tw tz ua ug uk us uy uz va vc ve vg vi vn vu wf ws xn xxx ye yt za zm zw);
But It throws errors:
1. Syntax error, near dm do dz
2. no such class mz, near "mw mx my mz"
ANy pointers on how to remove these errors?
If I use qw before that list it shows no errors, why? Whats wrong with the above declaration?

Answer 1

qw does quoting and separating for you.
my #foo = ( "bar", "baz" );
means the same as:
my #foo = qw( bar baz );
Having a stack of sequential unquoted values is just an error.
See the documentation for quote like operators.

Answer 2

The qw operator is a quoting operator, as are all of the other q* keywords (q qq qw qr qx) each takes a delimiting character (or pair in the case of braces) and treats everything within the delimiters as a string. Each of the operators do something different to the string, with qw splitting the string on whitespace to create a list.
When you write a series of barewords in Perl, you end up with a large nested chain of indirect object calls. Here is a short example without keywords (so that it is not a syntax error):
$ perl -MO=Deparse -e 'ac ad ae aero af ag ai al am an ao aq ar'
'ad'->ac('aero'->ae('ag'->af('al'->ai('an'->am('aq'->ao('ar'))))));
-e syntax OK
In your case, perl merrily went along parsing what looks like indirect object syntax until it encountered a keyword, which disrupted the chain and caused a syntax error.
If you had not used a keyword in your list, the code would have compiled fine, and then you would have gotten a runtime error about a missing method in a package. If you were running your code under the use strict; pragma (which you always should) then the final bareword would become a syntax error (since strict subs prevents promoting barewords to strings. That would have at least caught the error at compile time.
The important takeaway from this is that Perl has many quote-like operators that are effectively strings with special processing attached. Removing the quote-like operator will inevitably result in syntax errors, since arbitrarily formatted strings are not valid Perl. A list of the buitin quote-like operators can be found on the perlop manpage.

Answer 3

This is because when you omit qw/.../, your characters are treated as barewords, and when it comes to "do", which is a keyword, error is signaled.
EDIT: Even though my answer explains the reason of an error (well, I beleive so), #Quentin's suggestion is more constructive: do not use barewords (i.e. do use qw// in your example) to save your time catching errors like yours. For example, you have int in your list, which is also a keyword, lc (a function), etc.