Something

#! /usr/bin/perl

use strict;
use warnings;

use Getopt::Std;

our($opt_r, $opt_v);
getopts('rv');

my %objs;
my %syms;
my %depsyms;
my %objdefs;

open NM, "nm -Ag @ARGV |" or die "$!";

while(<NM>){
    /^(.*:)?(.*):[[:xdigit:] ]+([A-Z])\s+(.*)$/ or next;
    my($obj, $type, $sym) = ($2, $3, $4);
    if($type eq 'U'){
        $objs{$obj}{$sym}++;
        $depsyms{$sym}{$obj}++;
    } else {
        @{$objs{$obj}}{()} = ();
        $syms{$sym} = $obj;
        $objdefs{$obj}{$sym}++;
    }
}

close NM;

for my $obj (sort keys %objs) {
    my %deps;

    if (!$opt_r) {
        for my $sym (keys %{$objs{$obj}}) {
            next if not defined $syms{$sym};
            $deps{$syms{$sym}}{$sym}++;
        }
    } else {
        for my $sym (keys %{$objdefs{$obj}}) {
            next if not defined $depsyms{$sym};
            for my $o (keys %{$depsyms{$sym}}) {
                map $deps{$o}{$_}++,
                  grep defined $objdefs{$obj}{$_}, keys %{$objs{$o}};
            }
        }
    }

    print "$obj:\n";
    for my $dep (sort keys %deps) {
        print "\t$dep\n";
        $opt_v and print "\t\t$_\n" for sort keys %{$deps{$dep}};
    }
}