The problem is that the list ($a .. ++$a) is not evaluating a list like you think it is. It is not doing:

$start = $a;
$end = ++$a;
for ($_ = $start; $_ <= $end; $_++) { ... }
[download]

But rather, it is evaluating its endpoints, and then constructing the list from that. That is the cause of your problem:

for (++$x .. $x++ . $x) { ... }
# starting at ++$x
# ending at $x++ . $x
# THE END HAS MODIFIED THE START
[download]

You can witness a similar result from:

print ++$x, ++$x, ++$x;  # 333
[download]

You see, the arguments to a function aren't copies of the variables, but rather aliases -- by modifying ONE of the $x's, you've modified the others as well.

Knowing this, the output of this program makes sense to me:

$x = 3;
print ++$x/$x--;  # 3/4 => 0.75
[download]

Why is that? Well, the numerator is ++$x, and the denominator is $x--; but in subtracting 1 from $x in the denominator, we have now altered the numerator back to its original state!

I've worked out a solution to your 1 .. 12 loop, then.

for (++$x .. $x++ . $x--) { ... }
# or
for (++$....$.++.$.--) { ... }
[download]

See if you can work out why the starting point is 1.

japhy -- Perl and Regex Hacker

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

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! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

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

Outside of code tags, you may need to use entities for some characters:

	For:		Use:
	&		&
	<		&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.