> (can I rely on this behaviour of simplifying the number?)

It depends on what you think the "complicated" number is.

Many decimal fractions can't be represented without a tiny loss as binary floats.°

But print rounds the last digit(s) before output so it'll look accurate at first, 

  DB<80> $x = 1.100000000000;

  DB<81> print $x
1.1

[download]

even if it's internal representation is flawed.°

  DB<84> printf '%0.16f', 1.1
1.1000000000000001

[download]

but as soon as the rounding error exceeds print's tolerance, you'll get bitten

  DB<82> $x += 1.1 for 1..55;

  DB<83> print $x
61.6000000000001

[download]

So, yes you can mostly rely on it, if the number was never part of arithmetic operations which accumulated rounding errors.

BUT you should know that the print wasn't just cutting off trailing zeros but also rounding to achieve this.

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery

update

°) Some simple rational numbers (e.g., 1/3 and 1/10) cannot be represented exactly in binary floating point, no matter what the precision is. ... Software packages that perform rational arithmetic represent numbers as fractions with integral numerator and denominator, and can therefore represent any rational number exactly....

It's an inherent problem of floating point arithmetic. Not many languages offer alternatives to avoid this "flaw" with rational numbers. (Raku seems to be one of the exceptions here). NB: But this won't help with non-rational numbers like Pi or sqrt(2).

In reply to Re: Perl 5 numeric type and simplifications (updated) by LanX
in thread Perl 5 numeric type and simplifications by pango

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