Hi Lotus1,

The last if !line; part will never do anything even if corrected

Turns out I missed it yesterday - the line does do something:

$ perl -wMstrict -n
my $line = $_ if /\bWood\b/;
chomp ($line);
print "BANG!\n" if !$line;
__END__
Hello, Wood World
Foobar

[download]

Outputs:

Use of uninitialized value $line in scalar chomp at - line 2, <> line 
+2.
BANG!

[download]

The ... if !$line gets triggerd when $line is false, which is a case that can happen.

There's another thing I missed yesterday: my $line = $_ if /\bWood\b/;, to which perlsyn has to say this:

NOTE: The behaviour of a my, state, or our modified with a statement modifier conditional or loop construct (for example, my $x if ...) is undefined. The value of the my variable may be undef, any previously assigned value, or possibly anything else. Don't rely on it. Future versions of perl might do something different from the version of perl you try it out on. Here be dragons.

So really, that entire loop body needs a rewrite, maybe:

while (<$fh>) {
    chomp;
    next unless /\bWood\b/;
    ...
}

[download]

Regards,
-- Hauke D

In reply to Re^3: Print hash keys and lookup ... by haukex
in thread Print hash keys and lookup the keys for values in another filr by Magnolia25

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.