Parameters can't contain the NUL character. Your so-called working code breaks if you change 2.4 to 2.5 (which generates at least one a NUL byte).

I recommend that you pass the hex of the packed string. You could also use base64, JSON, etc, etc, etc.

Furthermore, you have a code-injection bug. "'$p'" is not an appropriate way to generate a Perl string literal. $p could easily contain byte 0x27 (single quote). A trailing byte 0x5C (backslash) would also be problematic.

I recommend that you pass the value as an argument. 

use strict;
use warnings;
my $template = 'd<';
my $nv = 2.5;
my $p = pack $template, $nv;

system $^X, '-wle', 'print $ARGV[0]', unpack('H*', $p);

[download]

Seeking work! You can reach me at ikegami@adaelis.com

In reply to Re: pack() returns an unusable string by ikegami
in thread pack() returns an unusable string by syphilis

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.