[inseparable changes from patch from perl5.003_17 to perl5.003_18]

[p5sagit/p5-mst-13.2.git] / pod / perldiag.pod

diff --git a/pod/perldiag.pod b/pod/perldiag.pod
index 49d30fc..6e4a3cf 100644 (file)
--- a/pod/perldiag.pod
+++ b/pod/perldiag.pod
@@ -1815,7 +1815,7 @@ shifting or popping (for array variables).  See L<perlform>.
 
 =item Scalar value @%s[%s] better written as $%s[%s]
 
-(W) You've used an array slice (indicated by @) to select a single value of
+(W) You've used an array slice (indicated by @) to select a single element of
 an array.  Generally it's better to ask for a scalar value (indicated by $).
 The difference is that C<$foo[&bar]> always behaves like a scalar, both when
 assigning to it and when evaluating its argument, while C<@foo[&bar]> behaves
@@ -1827,6 +1827,20 @@ element as a list, you need to look into how references work, because
 Perl will not magically convert between scalars and lists for you.  See
 L<perlref>.
 
+=item Scalar value @%s{%s} better written as $%s{%s}
+
+(W) You've used a hash slice (indicated by @) to select a single element of
+a hash.  Generally it's better to ask for a scalar value (indicated by $).
+The difference is that C<$foo{&bar}> always behaves like a scalar, both when
+assigning to it and when evaluating its argument, while C<@foo{&bar}> behaves
+like a list when you assign to it, and provides a list context to its
+subscript, which can do weird things if you're expecting only one subscript.
+
+On the other hand, if you were actually hoping to treat the hash
+element as a list, you need to look into how references work, because
+Perl will not magically convert between scalars and lists for you.  See
+L<perlref>.
+
 =item Script is not setuid/setgid in suidperl
 
 (F) Oddly, the suidperl program was invoked on a script with its setuid
@@ -2349,6 +2363,14 @@ L<perlref> for more on this.
 (W) A copy of the object returned from C<tie> (or C<tied>) was still
 valid when C<untie> was called.
 
+=item Value of %s may be "0"; use "defined"
+
+(W) In a conditional expression, you used <HANDLE>, <*> (glob), or
+C<readdir> as a boolean value.  Each of these operators may return a
+value of "0"; that would make the conditional expression false, which
+is probably not what you intended.  So, when using these operators in
+conditional expressions, test their values with the C<defined> operator.
+
 =item Variable "%s" is not exported
 
 (F) While "use strict" in effect, you referred to a global variable