Although there's undoubtedly a perl module out there doing what you want to do from the looks of it (and it's likely to be HTML::Entities), here's some code to help you on your way

my %iso8859 = (
    "\xA0" => ' ',  
    "\xA1" => '¡', 
    "\xA2" => '¢',  
    "\xA3" => '£', 
    "\xA4" => '¤',
    "\xA5" => '¥',   
    "\xA6" => '¦',
);

my $string = "a £ a penny";
my $regex  = join '|', map quotemeta, keys %iso8859;
$string =~ s/($regex)/$iso8859{$1}/g;
print $string;

__output__

a £ a penny
[download]

You may not need the quotemeta() in the map() but I've just added it 'just in case'.
HTH

_________
broquaint