Simplest I think is to just post the canonical example that I run across again and again... I would dearly like this to be all on one line for concision and clarity: 

 
  (my @v = keys %foo) == 1 or die "Got more than one: @v\n";
  print "V:@v\n";

[download]
This gives: 
Possible unintended interpolation of @v in string...
Global symbol "@v" requires explicit package name...

[download]

It's the scoping of the parentheses around the my assignment that causes the problem. If I leave out @v from the error message, the logic is correct and everything works: @v, if assigned to successfully, is correctly set and visible for the print statement. I'm trying to avoid doing work twice (repeating the call to keys in the error message).

The ugly alternative is to move my @v outside the comparison, but it just looks clunky and messes up a nice column of assignments. It's not just hash checking, it could be anything: 

 my $x = parse_thing();
 my $y = $x->{item} or die "Item not found in x.\n";
 my @z; (@z = do_xyz()) < 3 or die "Got extra Z: @z\n";
 print "Z:@z\n";

[download]

This has been bugging me for years, and I'm resigned to it, just wondering if there was a clever way around it.

Thanks!

In reply to Declaring with my, assigning, and testing in same line by mordibity

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.