Another variation with Getopt::Long and hash tables to declare the defaults:

#!/usr/bin/perl -w
use strict;
use Getopt::Long;

my ($verb, $obj) = $0 =~ m|([^/]+)-([^/]+)$|;

my %defaults_verbs = (
    'create' => {
        foo => "foo",
        bar => "",
    },
    'update' => {
        foo => "",
        bar => "bar",
    },
    #...
);
my %defaults_objs = (
    'tap' => {
        baz => 42,
    },
    'fap' => {
        baz => 99,
    },
    #...
);
my %defaults_combined = (
    'create-tap' => {
        foo => "boo",
        baz => 13,
    },
    #...
);

# merge individual defaults hashrefs (order matters), e.g.:
my $opts = {
    %{ $defaults_verbs{$verb}            //{} },
    %{ $defaults_objs{$obj}              //{} },
    %{ $defaults_combined{"$verb-$obj"}  //{} },
};

GetOptions($opts, 'foo=s', 'bar=s', 'baz=i');

for my $opt (sort keys %$opts) {
    print "$opt=$opts->{$opt}\n";
}
[download]

$ for name in create-tap update-tap ; do ln -s 882180.pl $name ; done

$ ./create-tap
bar=
baz=13
foo=boo

$ ./create-tap --foo=FOO
bar=
baz=13
foo=FOO

$ ./update-tap
bar=bar
baz=42
foo=

$ ./update-tap --baz=55
bar=bar
baz=55
foo=
[download]