In this case it's probably easier to use a stack and a loop rather than recursion. Consider:

use warnings;
use strict;

my $sql = <<SQL;
select A, B, C,
  (select D, E, F,
    (select G, H from AA where ID = Z) from BB where ID2 = X),
      I, J
        from CC;
SQL

my @parts = split /(\W+)/, $sql;
my @formatting = (undef);

for my $part (@parts) {
    print $part;

    if (lc $part eq 'select') {
        $formatting[-1] = 1;
        next;
    }

    if (lc $part eq 'from') {
        $formatting[-1] = undef;
        next;
    }

    if ($part =~ m'\)') {
        pop @formatting;
    }

    next if ! $formatting[-1];

    if ($part =~ m'\(') {
        push @formatting, undef;
        next;
    }

    print qq{ format \\"\%s|\\"} if $part =~ /\w/;
}

[download]

Prints:

select A format \"%s|\", B format \"%s|\", C format \"%s|\",
  (select D format \"%s|\", E format \"%s|\", F format \"%s|\",
    (select G format \"%s|\", H format \"%s|\" from AA where ID = Z) f
+rom BB where ID2 = X),
      I format \"%s|\", J format \"%s|\"
        from CC;

[download]
True laziness is hard work

In reply to Re: Recursive parse - by GrandFather
in thread Recursive parse - by real.aussie

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