Character shift to encode string

[Mark G. Franz]

Posted for a friend, this is his message;   I need to encript my CGI form URL that is enerated thru a perl script "page1.cgi". The URL that the CGI script generates is like: "name=me&ph=1234" To enscript the above, one suggested me to use character shift to encode the above URL. a->c, b->d, p->r etc.. I tried this. But never thought it is so tough. I could write the 1st function, enc() that changes a->c, n->p, y->a.. but when I try to write dec() that does the reverse, $var = "m"; $var--; does not work.. I cannot find any C like char to int conversion function. please help... thanks.Su $a="pqr"; $b=enc($a); print "$b\n"; //prints "rst" ...ok but sub enc { my $temp=shift; my $ret=''; @temp_array=split(//, $temp); my $len=@temp_array; for (my $i=0; $i<$len; $i++) {    if ($temp_array[$i] eq "y")    {    $temp_array[$i]="a";    }    elsif ($temp_array[$i] eq "z")    {    $temp_array[$i]="b";    }    else    {    $temp_array[$i]++;#works..    $temp_array[$i]++;#works..    #But $temp_array[$i]--; does NOT work!!!    } $ret="$ret$temp_array[$i]"; } return($ret); }