#!/usr/bin/env perl

use Getopt::Long;

GetOptions(\my %h
    ,qw(a:s b c d)
    ,qw(e=s f g h)
    ,qw(i:o j k l m n)
    ,qw(o=o p q r s t)
    ,qw(u:f w x)
    ,qw(y=f z)
    );

### dump: %h
### 'Order them ...'
my $command_line;
for my $option ('a'..'z') {
    $command_line.="$option "
        if (exists $h{$option});
    }
### dump: $command_line
### 'Parse $command_line with a regex ...'
if ($command_line !~ m{^(\ba\b( [b..d])|e|i|o|u|y) $}) { # conflicting options
    die "Conflicting options in '$command_line'!";
    }
    
### "We're good to go with '$command_line'!"
exit;