Which comparative operator should I use?

dead_passive has asked for the wisdom of the Perl Monks concerning the following question:

I am using CGI to accept some input to my script -

if ($cgi->param('Students') eq 'Add') {
    print "ADDING<br>\n";
    for ($i = 1; $i < 6; $i++) {
        $paramname = "Name" . $i;
        print $paramname . " = " . $cgi->param($paramname) . "<br>\n";
        if ($cgi->param($paramname) != "") {
            print "GSFDSFDS";
            $insertvalue = $cgi->param($paramname);
            print $insertvalue;
            #$dbh->do("insert into Students (Name) values ($insertvalu
+e)");
            #$dbh->disconnect;
            
        }
    }
[download]

The 'if ($cgi->param($paramname) != "")' never gets executed even though just prior to it $cgi-param($paramname) is printed successfully. I am using CGI input elsewhere in the script and it works fine. I really can't see what the problem is here and I would really appreciate some help.
Thanks
J.Britton

20040220 Edit by BazB: Changed title from 'Accepting CGI Input'

Comment on Which comparative operator should I use? Download Code

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Re: Which comparative operator should I use? by Skeeve (Parson) on Feb 19, 2004 at 12:34 UTC
`!=` is for numbers `ne` for strings	[reply] [d/l] [select]
Re: Which comparative operator should I use? by Abigail-II (Bishop) on Feb 19, 2004 at 12:38 UTC
Of course the `if ($cgi->param($paramname) != "")` gets executed. It just has a different result than you expect. `!=` is a numerical comparison operator, and hence, turns both it operands into numbers. `""` becomes `0`. `$cgi->param($paramname)` is very likely to be a string not starting with a number, and will hence become `0` as well. Which results in `0 != 0`, which is false. If you turn on warnings, Perl will warn you that this is happening. Abigail	[reply]