#!/usr/bin/env perl -l

use strict;
use warnings;

my %lookup = ('500' => '000', '0 988' => '000', '0 1210' => '1000');
my $re = '(' . join('|' => keys %lookup) . ')';

my $string = 'www "999" xxx "0 1210" yyy "500" zzz "0 988"';
print $string;

$string =~ s/$re/$lookup{$1}/g;
print $string;

##</code><code>##

www "999" xxx "0 1210" yyy "500" zzz "0 988"
www "999" xxx "1000" yyy "000" zzz "000"