The perlsyn doc on statment modifiers says that a line such as my $var = 1 if $test; leads to an undefined behaviour: you don't know what happens to the variable if the condition evaluates to false.

Are you sure of that? This is not what I understand from the document you quote. My understanding, from reading aforesaid document, is that my $var if $test; is undefined. But this is quite different. Please note that this is not a troll at all, I would really like to know. Although, in such a case, I would normally declare the variable and assign it in separate instructions, I think there might be some of my programs (at most very few) where I used something equivalent to my $var = 1 if $test; and I don't recall having encountered any problem with this type of syntax (but it is also quite possible that I actually never did it, I would in principle be suspicious with such a construct with conditional declaration).

This seems to work according to my expectations: 

$ perl -e 'my $c = 1 if 1; print $c;'
1
~
$ perl -e 'my $c = 1 if 0; print $c;'

[download]

In reply to Re^2: postfix syntax enlightenment by Laurent_R
in thread postfix syntax enlightenment by RobertCraven

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.