#!/usr/bin/perl

my %YES;
my %NO;

$a='pat http://www.abc.com/test.gif ma http://www.abc.com/hello.html http://www.abc.com/test.gif ';

$a=~s{(http://[\w\.\-\?\&\;\#\/]+)}{&ask($1)}gexi;

sub ask{
	my($url) =@_;
	return $url unless index($url,'www.abc.com');
# add more "return $url if condition;" here (blacklist)
	if($YES{$url}){
		$url =~ s/www.abc.com/www.test.com/;
		return $url;
	}elsif($NO{$url}){
		return $url;
	}else{
		print  "substitute $url ?";
		$ans = <STDIN>;
		if($ans =~ m/y/i){
			++$YES{$url};
		}else{
			++$NO{$url};
		}
		return ask($url);
	}
}