Even so if you change lib=s to lib=f and then use the following command it still does not complain (and error out since lib should be a float)

It's not an error because of pass_through. It causes anything wrong to left in @ARGV for further processing. For example, 

use Getopt::Long (); 

our $opt_float;

Getopt::Long::Configure('no_auto_abbrev','pass_through');
Getopt::Long::GetOptions('float=f')
   or die("Bad args\n");

print("\$opt_float = ", defined($opt_float) ? $opt_float : "[undef]", 
+"\n");
print("\@ARGV      = ", join(' ', @ARGV), "\n");

[download]

returns 

>perl 551380.pl -float 1.3
$opt_float = 1.3
@ARGV      =

>perl 551380.pl -float abc
$opt_float = [undef]
@ARGV      = -float abc

[download]

In reply to Re^2: Issues w/ getOptions parsing options with pass_through enabled by ikegami
in thread Issues w/ getOptions parsing options with pass_through enabled by Brawny1

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