** Start of listing of h4int-perl.cgi **
#!/usr/bin/perl
use CGI qw(:standard);

print "Content-type: text/plain;charset=us-ascii\n\n";

# Check if string contains integer, possibly surrounded by whitespace.
# Returns "" if OK, otherwise a string explaining the problem.
sub strcheckint {
    my($str) = $_[0];
    if ($str =~ m/^ *[-+]?[0-9]+ *$/) {
	return(""); # Good!
    }
    elsif (!($str =~ m/[0-9]+/)) {
	return("Not any digit anywhere.");
    }
    elsif ($str =~ m/^ *[-+][^0-9]+/) {
	return("Sign, but then no digit immediately.");
    }
    elsif ($str =~ m/^ *[-+]?[0-9]+.*[^ 0-9]+/) {
	return("Valid number, but then garbage later.");
    }
    elsif ($str =~ m/^ *[-+]?[0-9]+ *[^ ]+/) {
	return("Valid number, then whitespace, but then another digit.");
    }
    elsif ($str =~ m/^ *[^ 0-9]+.*[0-9]+/) {
	return("Garbage before the first digit.");
    }
    else {
	return("Stub: Something else bad.");
    }
}

sub keygetcheckint {
    my($key) = $_[0];
    $fn = param($key);
    print("In form-field ["); print($key); print("] we have value [");
    print($fn); print("]: ");
    my($res) = strcheckint($fn);
    if ($res =~ m/^$/) { # That should match empty string only
	$n = 0+$fn;
	print("Good! The number is ["); print($n); print("].\n");
	print("The next larger numbers are: "); print($n+1); print(" ");
	print($n+2); print(" "); print($n+3); print("\n");
    }
    else {
	print("Bad: "); print($res); print("\n");
    }
}

keygetcheckint('num1');
keygetcheckint('num2');
keygetcheckint('num3');
keygetcheckint('num4');
keygetcheckint('num5');
keygetcheckint('num6');
keygetcheckint('num7');
keygetcheckint('num8');

#What's left of old test loop on stdio:
#while (1) {
#    print("Type in a number:");
#    $inputline = <STDIN>;
#    print("You typed ["); print($inputline); print("].\n");
#    chomp($inputline);
#    print("After trim, we now have ["); print($inputline); print("].\n");
#    if(strcheckint($inputline)==0) {
#    }
#}
** End of listing of h4int-perl.cgi **

Here is the directory entry for that file:
-rwx------  1 rem  user  1924 Feb 28  2007 h4int-perl.cgi
   ^ Note user execute permission needed for all CGI scripts.