my $open = 0;      
my $comma = 0;  
LOOP: while ($test =~ /(.)/g) {          
    my $char = $1;    
    if ($char eq '[' or $char eq ']') {               
        $open = $char eq '[' ? 1 : 0;           
        $comma = 0 if ($char = ']');  
    }           
    else {             
        if ($char eq ',' and $open == 0) {                     
            print "INVALID";                 
            last LOOP;             
        }     
        elsif ($char eq ',' and $open == 1) {  
            $comma = 1;  
        }      
    }     
}   
print "INVALID" if ($open and $comma);