You don't get a warning when undef is interpreted as the identity element of the operator. Or, in other words, when the following pattern isn't useless
while (condition) # or for loop
$value <op>= something;
$sum += $_ for @nums;
next if /INVALID/;
$valid .= $_;
And not setting the variable before the loop let's you tell if there were no valid lines at all, or if the only valid data was empty strings (or $sum will be undef
rather than 0 if there are no numbers).
On the other hand you can use whatever values you want, this will never yield anything but 0:
$product *= $_ for @nums;
This can only be a mistake.
So this would tend towards "this a right thing to do", but I couldn't find the documentation either.
Edit: that was full of typos. I wrote "under" for "undef", "is" for "if" and "identify" for "identity". I hope I got them all...
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:
You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
- a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, 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, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
Link using PerlMonks shortcuts! What shortcuts can I use for linking?
See Writeup Formatting Tips and other pages linked from there for more info.
| & || & |
| < || < |
| > || > |
| [ || [ |
| ] || ] ||