There are many ways...

sub getchar_unpack {
    my ($string, $index) = @_; 
    return unless $index >= 0 and $index < length($string); 
    return chr( (unpack 'C*', $string)[$index] );
}

sub getchar_split {
    my ($string, $index) = @_; 
    return unless $index >= 0 and $index < length($string); 
    return ( (split //, $string)[$index] );
}

sub getchar_loop {
    my ($string, $index) = @_; 
    return unless $index >= 0 and $index < length($string); 
    $string = reverse $string; 
    my $c; 
    $c = chop $string until $index-- == 0; 
    return $c;    
}
[download]

But why?

-sauoq
"My two cents aren't worth a dime.";