Two people trying to add the same surname simultaneously is already handled because add_surname.cgi first checks if an entry already exists for the surname in question.
This makes two people adding the same surname less likely, but not impossible. Imagine your code is like this: 
1. Check if surname exists
2. Add surname
and you have two clients, Alice and Bob, both adding the same surname. If things happen to be ordered like this: 
Alice: Check if surname exists (it doesn't)
  Bob: Check if surname exists (it doesn't)
Alice: Add surname
  Bob: Add surname
you'll have the same problem. One solution is to enforce only a single surname in the database, with UNIQUE constraints on columns.

In reply to Re: Executing a Script to Completion by sgifford
in thread Executing a Script to Completion by Baz

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.