#!/usr/bin/perl
use strict;
use warnings;

my %hoh = (
    bar => {value => 42},
    baz => {value => 199},
    foo => {value => 3},
);

my $joe = shift @ARGV;

my $sortfunctions = {
    numbers => sub { $hoh{$a}{value} <=> $hoh{$b}{value} },
    letters => sub { $hoh{$a}{value} cmp $hoh{$b}{value} },
};
my $sortfunc = $sortfunctions->{$joe};

foreach my $key (sort $sortfunc keys %hoh) {
    print "$key: $hoh{$key}{value}\n";
}

__END__
$ ./818578.pl letters
baz: 199
foo: 3
bar: 42
$ ./818578.pl numbers
foo: 3
bar: 42
baz: 199