#!/usr/bin/perl -w
use strict;
 
for my $str (  @ARGV  ) {
    my @stack;
    my $list= [];
    for my $s (  $str =~ m/[()]|[^()]+/g  ) {
        if(  '(' eq $s  ) {
            push @stack, $list;
            push @$list, [];
            $list= $list->[-1];
        } elsif(  ')' eq $s  ) {
            if(  ! @stack  ) {
                die "Unmatched ')'";
            }
            $list= pop @stack;
        } else {
            push @$list, $s;
        }
    }
    if(  @stack  ) {
        die 0+@stack, " unclosed '('s";
    }
    warn "Done.\n";
}