You could decouple the parsing and building steps, as nothingmuch suggested: 

sub parse_brackets {
  my @out;
  
  foreach my $line ( @_ ) {
    $line_no ++;
    $line =~ s/\A\s+//;
    $line =~ s/\s+\Z//;
    if ( $line !~ /\S/ ) {
      next;
    } elsif ( $line =~ s/\s*\{$// ) {
      push @out, 'open' => [ split ' ', $line ];
    } elsif ( $line eq '}' ) {
      push @out, 'close' => 1;
    } else {
      push @out, 'line' => $line;
    }
  }
  return @out;
}

sub build_brackets {
  my @parse;
  my @stack = \@parse;
  
  while ( scalar @_ ) {
    my ( $type, $value ) = splice( @_, 0, 2 );
    if ( $type eq 'open' ) {
      my %node = ( type => shift(@$value), ( @$value ? ( name => shift
+(@$value) ) : () ) );
      push @{ $stack[0] }, \%node;
      unshift @stack, do { $node{contents} = [] };
    } elsif ( $type eq 'close' ) {
      shift @stack; 
      scalar @stack or die("Too many right brackets");
    } else {
      push @{ $stack[0] }, $value;
    }
  }
  scalar @stack == 1 or die("Too few right brackets");

  return @parse;
}

use Data::Dumper;

print Dumper( build_brackets( parse_brackets( @lines ) ) );

[download]

I'm not sure this is a big win for your case, but if you need the extra flexiblity...

In reply to Re^3: Parsing a macro language by simonm
in thread Parsing a macro language by bluetrust

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