There are potentially other small improvements. You could drop:

$query =~ s/[\n\r\f]+/ /g;
[download]

since you already collapsed whitespace on the line before.

You might get better performance out of:

$query =~ s/(["']).*?\1/S/g;
[download]

by replacing it with:

$query =~ s/"[^"]*"/S/g;
$query =~ s/'[^']*'/S/g;
[download]

This avoids capturing characters which may or may not help. Also, you could potentially handle double quoted (") strings earlier in the sequence of regexen if that would reduce the number of potential real number strings exposed to your regex for real numbers and floats.

Finally, in:

$query =~ s{
             \b(in|values?)\s*\(\s*([NS])\s*,[^\)]*\)
           }
           {$1($2+)}gx;
[download]

You can take advantage of the fact that you have already normalized whitespace:

$query =~ s{
             \b(in|values?) *\( *([NS]) *,[^\)]*\)
           }
           {$1($2+)}gx;
[download]

---

---

• Are you posting in the right place? Check out Where do I post X? to know for sure.
• Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:

  <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>

• Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
• Want more info? How to link or How to display code and escape characters are good places to start.