for (values %copy) {
    1 while                              # repeat till no replacement left
        s/^($pattern)/$h_orig->{$1}/g; 
}

##</code><code>##

use strict;
use warnings;
use Data::Dump qw/pp dd/;

my $h_orig =
  {
  '/a/b/c/dt/data/SUSE/tool/0.9.0' => '/a/b/c/dt/tools/SUSE/tool/0.9.0',
  '/nfs/us' => '/usr/bin',
  '/a/b/c' => '/nfs/us'
  };


my $pattern = join "|", map quotemeta, keys %$h_orig;

my %copy = %$h_orig;

for (values %copy) {
    1 while s/^($pattern)/$h_orig->{$1}/g; 
}

pp $h_orig, \%copy;


##</code><code>##

-*- mode: compilation; default-directory: "d:/tmp/pm/" -*-
Compilation started at Sun Feb  6 15:59:06

C:/Strawberry/perl/bin\perl.exe -w d:/tmp/pm/replace_pat2.pl 
(
  {
    "/a/b/c" => "/nfs/us",
    "/a/b/c/dt/data/SUSE/tool/0.9.0" => "/a/b/c/dt/tools/SUSE/tool/0.9.0",
    "/nfs/us" => "/usr/bin",
  },
  {
    "/a/b/c" => "/usr/bin",
    "/a/b/c/dt/data/SUSE/tool/0.9.0" => "/usr/bin/dt/tools/SUSE/tool/0.9.0",
    "/nfs/us" => "/usr/bin",
  },
)

Compilation finished at Sun Feb  6 15:59:06