... you can get accurate calculations by adding a use bignum; to your code

I think this is the only solution that requires no modification to the original line of code:
for ($x=0.8; $x > 0.1; $x -= 0.01) { print "$x\n"; }

It's probably worth pointing out to the OP that it works simply because bignum uses decimal (base 10) arithmetic.

There are other ways to force base 10 arithmetic - eg Math::Decimal, Math::Decimal64 and Math::Decimal128. (The last 2 are a plug, and will work far more quickly than bignum.)
However, they would all require some changes to the given line of code. For example: 
use Math::Decimal64;
for ($x = Math::Decimal64->new('0.8'); $x > '0.1'; $x -= '0.01') { pri
+nt "$x\n"; }
# or if one is insistent upon receiving 0.xx formatting of the values 
+(instead of "xxe-2") formatting:
for ($x = Math::Decimal64->new('0.8'); $x > '0.1'; $x -= '0.01') { pri
+nt "$x" + 0, "\n"; }

[download]
Cheers,
Rob

In reply to Re^2: what did I just see..? by syphilis
in thread what did I just see..? by ishaybas

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.