I don't know XS very well, but if you want to create a scalar from a char * and return it to Perl, here's a way to do it in Inline (which is much easier than XS):

#!/usr/local/bin/perl
use strict;
use warnings;

use Inline C => <<'END_OF_C_CODE';
SV * get_string() {
    char string[] = "test";
    SV *result = newSVpv(string, 0);
    return result;
}
END_OF_C_CODE

my $string = get_string();
print $string;
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(It's a bit verbose for clarity)