Matching balanced parenthesis in Perl regex

Question

I have an expression which I need to split and store in an array:

aaa=\"bbb{ccc}ffffd\" { aa=\"bb,cc\" { a=\"b\", c=\"d\" } }, aaa=\"bbb{}\" { aa=\"b}b\" }, aa         


        

Answer 1

I agree with Scott Rippey, more or less, about writing your own parser. Here's a simple one:

my $in = 'aaa="bbb{ccc}ffffd" { aa="bb,cc" { a="b", c="d" } }, ' .
         'aaa="bbb{}" { aa="b}b" }, ' .
         'aaa="bbb,ccc"'
;

my @out = ('');

my $nesting = 0;
while($in !~ m/\G$/cg)
{
  if($nesting == 0 && $in =~ m/\G,\s*/cg)
  {
    push @out, '';
    next;
  }
  if($in =~ m/\G(\{+)/cg)
    { $nesting += length $1; }
  elsif($in =~ m/\G(\}+)/cg)
  {
    $nesting -= length $1;
    die if $nesting < 0;
  }
  elsif($in =~ m/\G((?:[^{}"]|"[^"]*")+)/cg)
    { }
  else
    { die; }
  $out[-1] .= $1;
}

(Tested in Perl 5.10; sorry, I don't have Perl 5.8 handy, but so far as I know there aren't any relevant differences.) Needless to say, you'll want to replace the dies with something application-specific. And you'll likely have to tweak the above to handle cases not included in your example. (For example, can quoted strings contain \"? Can ' be used instead of "? This code doesn't handle either of those possibilities.)