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