#! perl -slw
use strict;
use List::Util qw[ min ];
$|=1;

## Mildly cleaned up version with edgecase bug.

sub indexBal {
	my( $string, $lookFor, $limit ) = @_;
	my $nesting = 0;
	for( my( $position, $char ) = ( 0, substr $string, 0, 1 );
		$position < min( length( $string ) , $limit );
		$char = substr $string, ++$position, 1
	) {
		$nesting++ if $char =~ m/[\[\{]/;
		$nesting-- if $char =~ m/[\]\}]/;
		die 'Unbalanced' if $nesting < 0;
		return $position if $char eq $lookFor and $nesting == 0
	}
	return;
}

my $depth = 0;
my $indent = '    ';
my $string = '';
my $_print = sub {
	print $indent x $_[2], substr( $_[0], 0, $_[1], '' );
    $_[0] =~ s[^\s*][];
};

sub pp {
	my( $s, $max_width, $EOS ) = @_;
	$string .= $s;
	while( length( $string ) > $max_width or $EOS ) {

        my ($pos, $first ) = ( pos $string, $1 ) if $string =~ m/([\[\{\]\},])/g;
		return unless defined $pos;

        if ( defined $first and $first ne ',' ) {
            if ( $first =~ m/[\]\}]/ ) {
                $_print->( $string, ++$pos, --$depth );
            }
            elsif ( defined( my $newpos = indexBal( $string, $first eq '[' ? ']' : '}', $max_width ) ) ) {
                $_print->( $string, $newpos + 2, $depth );
			}
			else {
				$_print->( $string, $pos, $depth++ );
			}
        }
        else {
            $_print->( $string, $pos, $depth );
        }
	}
    return;
}

## Test harness only below here
my $data = <DATA>;

my $width = $ARGV[ 0 ]||100;
$indent = $ARGV[ 1 ] if @ARGV == 2;

while( length $data ) {
	my $p = 1+rindex( $data, ',', $width+rand( 50 ) )||length $data;
	my $sub = substr( $data, 0, $p, '' );
	pp( $sub, $width, !length $data );
}

__DATA__