-w is not actually equivalent to use warnings. The most obvious difference is that the warnings pragma is only available in perl5.6.0 and later.
The other, very important difference is that -w is global, while use warnings is lexical. -w will turn on warnings for all the code used by the script, including in other files. use warnings, on the other hand, will only enable warnings for the block in which it occurs. If you put use warnings in your main script, you won't get warnings from the modules that you use.
It is probably sufficient to recommend -w for new programmers; it works in all versions of Perl, and is the most general way of getting warnings.
Are you posting in the right place? Check out Where do I post X? to know for sure.
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big>
<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
<h1> <h2> <h3> <h4>
<h5> <h6> <hr /> <i>
<li> <nbsp> <ol> <p>
<small> <strike> <strong>
<sub> <sup> <table>
<td> <th> <tr> <tt>
Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
taken to ensure that their contents do not
have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
Want more info? How to link
or How to display code and escape characters
are good places to start.