use Encode;
use utf8;
#use open IO => ':locale';

#my $s = "El supersónico de los Indi ";
my $s1 = "El supero de los Indi ";

#$s1 = decode_utf8( $s);

print "\n\nStart string: $s1\n\n";

my $s2 = &fix_special_characters($s1);

print"\nEnd string: $s2\n\n";


sub fix_special_characters
{
my($string) = @_;

open(C,"<:utf8","chars.txt");
my @c = <C>;

for(my $i=0; $i < @c; $i++)
{
        my ($special,$htmlchar) = split(/\t/,$c[$i]);
        print "$special : $htmlchar";
        $string =~ s/$special/$htmlchar/ig;     ## this is generating the error message
}

return $string;
}

##</code><code>##

Start string: El supero de los Indi

Á    : &Aacute;
á    : &aacute;
É    : &Eacute;
é   : &eacute;
Í    : &Iacute;
í    : &iacute;
Ñ    : &Ntilde;
ñ    : &ntilde;
Ó   : &Oacute;
ó   : &oacute;
Ú    : &Uacute;
ú    : &uacute;
Ü    : &Uuml;
ü    : &uuml;
¿   : &iquest;
¡   : &iexcl;End string: El supero de los Indi


##</code><code>##

Malformed UTF-8 character (unexpected non-continuation byte 0x20, immediately after start byte 0xc1) in regexp compilation at sp.pl line 30, <C> line 16.
Malformed UTF-8 character (unexpected non-continuation byte 0x20, immediately after start byte 0xc1) in regexp compilation at sp.pl line 30, <C> line 16.