How about this? I am going to match every sql with $2 and print. Ignore $1. 

use strict;
use warnings;

while (<DATA>) {
    chomp;
    while (m/(--.*?$)              #that is comment
             |
             ((?:'[^']*'|[^'-]*))  #quated part of sql or ordinal part
            /xg) { #global, extended
        print $2 if $2;
    }
    print "\n";
}

__DATA__
select 'text' from foo        --This is a comment
select '--Not a valid comment' from foo        --But this is
select q from z -- as is this
select '--This is not a valid comment' from foo
select '--Not this' + '--either' from foo
select 'qaws' + make from "a" -- comment with 'a' quote
select 'a' from 'b' with 'c' -- comment with 'a --' comment
-- test comment (add1)
select 'text\'s' from foo        --escaped  ... (add2)
select 'text\'s' from foo        --escaped'  ... (add3)

[download]

I am not so confident with regex and add escaped test.
Then, add2 and add3 is not working well... sigh.

In reply to Re: Regex: Identifying comments by remiah
in thread Regex: Identifying comments by zuma53

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.