[0]  # cat parameter_check.pl
use v5.10;
use warnings;
use strict 'subs';
use feature 'state';
use Getopt::Std;

getopts("b:cd:",\%options);

if( exists $options{'b'} ){
    if( $options{'b'} ){
        say "option b $options{'b'}";
    }else{
        say "b is zero length string or equvalent";
    }
}else{
   say 'key b does not exist';
}
say "option c:", $options{'c'};
say "option d: ", $options{'d'};