ch33_01.htm

编程珍珠,里面很多好用的代码,大家可以参考学习呵呵,

<dt>
<b><tt class="literal">Can't ignore signal CHLD, forcing to default</tt></b>
</dt>
<dd>
<p>(W signal) Perl has detected that it is being run with the <tt class="literal">SIGCHLD</tt> signal
(sometimes known as <tt class="literal">SIGCLD</tt>) disabled.  Since disabling this signal
will interfere with proper determination of exit status of child
processes, Perl has reset the signal to its default value. This situation typically indicates that the parent program under
which Perl may be running (e.g., <em class="emphasis">cron</em>) is being very careless.</p>
</dd>


<dt>
<b><tt class="literal">Can't localize through a reference</tt></b>
</dt>
<dd>
<p>(F) You said something like <tt class="literal">local $$ref</tt>, which Perl can't currently
handle because when it goes to restore the old value of whatever <tt class="literal">$ref</tt>
pointed to after the scope of the <tt class="literal">local</tt> is finished, it can't be
sure that <tt class="literal">$ref</tt> will still be a reference.</p>
</dd>


<dt>
<b><tt class="literal">Can't localize lexical variable</tt> <em class="replaceable">%s</em></b>
</dt>
<dd>
<p>(F) You used <tt class="literal">local</tt> on a variable name that was previously declared as a
lexical variable using <tt class="literal">my</tt>.  This is not allowed.  If you want to
localize a package variable of the same name, qualify it with the
package name.</p>
</dd>


<dt>
<b><tt class="literal">Can't localize pseudohash element</tt></b>
</dt>
<dd>
<p>(F) You said something like <tt class="literal">local $ar-&gt;{'key'}</tt>, where <tt class="literal">$ar</tt> is
a reference to a pseudohash.  That hasn't been implemented yet, but
you can get a similar effect by localizing the corresponding array
element directly--<tt class="literal">local $ar-&gt;[$ar-&gt;[0]{'key'}]</tt>.</p>
</dd>


<dt>
<b><tt class="literal">Can't locate auto/</tt><em class="replaceable">%s</em><tt class="literal">.al in @INC</tt></b>
</dt>
<dd>
<p>(F) A function (or method) was called in a package that allows
autoloading, but there is no function to autoload.  Most probable causes
are a misprint in a function/method name or a failure to <tt class="literal">AutoSplit</tt>
the file, say, by doing <tt class="literal">make install</tt>.</p>
</dd>


<dt>
<b><tt class="literal">Can't locate</tt> <em class="replaceable">%s</em></b>
</dt>
<dd>
<p>(F) You said to <tt class="literal">do</tt> (or <tt class="literal">require</tt>, or <tt class="literal">use</tt>) a file that couldn't
be found. Perl looks for the file in all the locations mentioned in
<tt class="literal">@INC</tt>, unless the filename included the full path to the file. Perhaps you need to set the <tt class="literal">PERL5LIB</tt> or <tt class="literal">PERL5OPT</tt> environment variable
to say where the extra library is, or maybe the script needs to add
the library name to <tt class="literal">@INC</tt>.  Or maybe you just misspelled the name of
the file.</p>
</dd>


<dt>
<b><tt class="literal">Can't locate object method "</tt><em class="replaceable">%s</em><tt class="literal">" via package "</tt><em class="replaceable">%s</em><tt class="literal">"</tt></b>
</dt>
<dd>
<p>(F) You called a method correctly, and it correctly indicated a package
functioning as a class, but that package doesn't define that particular
method, nor does any of its base classes.</p>
</dd>


<dt>
<b><tt class="literal">Can't locate package</tt> <em class="replaceable">%s</em> <tt class="literal">for @</tt><em class="replaceable">%s</em><tt class="literal">::ISA</tt></b>
</dt>
<dd>
<p>(W syntax) The <tt class="literal">@ISA</tt> array contained the name of another package that
doesn't seem to exist.</p>
</dd>


<dt>
<b><tt class="literal">Can't make list assignment to \%ENV on this system</tt></b>
</dt>
<dd>
<p>(F) List assignment to <tt class="literal">%ENV</tt> is not supported on some systems,
notably VMS.</p>
</dd>


<dt>
<b><tt class="literal">Can't modify</tt> <em class="replaceable">%s</em> <tt class="literal">in</tt> <em class="replaceable">%s</em></b>
</dt>
<dd>
<p>(F) You aren't allowed to assign to the item indicated or otherwise try to
change it, such as with an autoincrement.</p>
</dd>


<dt>
<b><tt class="literal">Can't modify non-lvalue subroutine call</tt></b>
</dt>
<dd>
<p>(F) Subroutines meant to be used in lvalue context should be declared as
such.</p>
</dd>


<dt>
<b><tt class="literal">Can't modify nonexistent substring</tt></b>
</dt>
<dd>
<p>(P) The internal routine that does assignment to a <tt class="literal">substr</tt> was handed
a NULL.</p>
</dd>


<dt>
<b><tt class="literal">Can't msgrcv to read-only var</tt></b>
</dt>
<dd>
<p>(F) The target of a <tt class="literal">msgrcv</tt> must be modifiable to be used as a receive
buffer.</p>
</dd>


<dt>
<b><tt class="literal">Can't open</tt> <em class="replaceable">%s</em><tt class="literal">:</tt> <em class="replaceable">%s</em></b>
</dt>
<dd>
<p>(S inplace) The implicit opening of a file through use of the <tt class="literal">&lt;&gt;</tt>
filehandle, either implicitly under the <span class="option">-n</span> or <span class="option">-p</span> command-line
switches or explicitly, failed for the indicated reason.  Usually this
is because you don't have read permission for a file which you named
on the command line.</p>
</dd>


<dt>
<b><tt class="literal">Can't open bidirectional pipe</tt></b>
</dt>
<dd>
<p>(W pipe) You tried to say <tt class="literal">open(CMD, "|cmd|")</tt>, which is not
supported.  You can try any of several modules in the Perl library to
do this, such as <tt class="literal">IPC::Open2</tt>.  Alternatively, direct the pipe's output to
a file using <tt class="literal">&gt;</tt>, and then read it in under a different filehandle.</p>
</dd>


<dt>
<b><tt class="literal">Can't open error file</tt> <em class="replaceable">%s</em> <tt class="literal">as stderr</tt></b>
</dt>
<dd>
<p>(F) This is an error peculiar to VMS.  Perl does its own command-line
redirection, and it couldn't open the file specified after <tt class="literal">2&gt;</tt> or
<tt class="literal">2&gt;&gt;</tt> on the command line for writing.</p>
</dd>


<dt>
<b><tt class="literal">Can't open input file</tt> <em class="replaceable">%s</em> <tt class="literal">as stdin</tt></b>
</dt>
<dd>
<p>(F) This is an error peculiar to VMS.  Perl does its own command-line
redirection, and it couldn't open the file specified after <tt class="literal">&lt;</tt> on
the command line for reading.</p>
</dd>


<dt>
<b><tt class="literal">Can't open output file</tt> <em class="replaceable">%s</em> <tt class="literal">as stdout</tt></b>
</dt>
<dd>
<p>(F) This is an error peculiar to VMS.  Perl does its own command-line
redirection, and it couldn't open the file specified after <tt class="literal">&gt;</tt> or
<tt class="literal">&gt;&gt;</tt> on the command line for writing.</p>
</dd>


<dt>
<b><tt class="literal">Can't open output pipe (name:</tt> <em class="replaceable">%s</em><tt class="literal">)</tt></b>
</dt>
<dd>
<p>(P) This is an error peculiar to VMS.  Perl does its own command-line
redirection, and it couldn't open the pipe into which to send data
destined for <tt class="literal">STDOUT</tt>.</p>
</dd>


<dt>
<b><tt class="literal">Can't open perl script "</tt><em class="replaceable">%s</em><tt class="literal">":</tt> <em class="replaceable">%s</em></b>
</dt>
<dd>
<p>(F) The script you specified can't be opened for the indicated reason.</p>
</dd>


<dt>
<b><tt class="literal">Can't redefine active sort subroutine</tt> <em class="replaceable">%s</em></b>
</dt>
<dd>
<p>(F) Perl optimizes the internal handling of sort subroutines and keeps
pointers into them.  You tried to redefine one such sort subroutine when it
was currently active, which is not allowed.  If you really want to do
this, you should write <tt class="literal">sort { &amp;func } @x</tt> instead of <tt class="literal">sort func @x</tt>.</p>
</dd>


<dt>
<b><tt class="literal">Can't remove</tt> <em class="replaceable">%s</em><tt class="literal">:</tt> <em class="replaceable">%s</em><tt class="literal">, skipping file</tt></b>
</dt>
<dd>
<p>(S inplace) You requested an inplace edit without creating a backup
file.  Perl was unable to remove the original file to replace it with
the modified file.  The file was left unmodified.</p>
</dd>


<dt>
<b><tt class="literal">Can't rename</tt> <em class="replaceable">%s</em> <tt class="literal">to</tt> <em class="replaceable">%s</em><tt class="literal">:</tt> <em class="replaceable">%s</em><tt class="literal">, skipping file</tt></b>
</dt>
<dd>
<p>(S inplace) The rename done by the <span class="option">-i</span> switch failed for some reason,
probably because you don't have write permission to the directory.</p>
</dd>


<dt>
<b><tt class="literal">Can't reopen input pipe (name:</tt> <em class="replaceable">%s</em><tt class="literal">) in binary mode</tt></b>
</dt>
<dd>
<p>(P) An error peculiar to VMS.  Perl thought <tt class="literal">STDIN</tt> was a pipe, and tried to
reopen it to accept binary data.  Alas, it failed.</p>
</dd>


<dt>
<b><tt class="literal">Can't reswap uid and euid</tt></b>
</dt>
<dd>
<p>(P) The <tt class="literal">setreuid</tt> call failed for some reason in the setuid emulator
of <em class="emphasis">suidperl</em>.</p>
</dd>


<dt>
<b><tt class="literal">Can't return outside a subroutine</tt></b>
</dt>
<dd>
<p>(F) The <tt class="literal">return</tt> statement was executed in mainline code, that is, where
there was no subroutine call to return out of.</p>
</dd>


<dt>
<b><tt class="literal">Can't return</tt> <em class="replaceable">%s</em> <tt class="literal">from lvalue subroutine</tt></b>
</dt>
<dd>
<p>(F) Perl detected an attempt to return illegal lvalues (such
as temporary or readonly values) from a subroutine used as an lvalue. This is not allowed.</p>
</dd>


<dt>
<b><tt class="literal">Can't stat script "</tt><em class="replaceable">%s</em><tt class="literal">"</tt></b>
</dt>
<dd>
<p>(P) For some reason, you can't <tt class="literal">fstat</tt> the script even though you have
it open already.  Bizarre.</p>
</dd>


<dt>
<b><tt class="literal">Can't swap uid and euid</tt></b>
</dt>
<dd>
<p>(P) The <tt class="literal">setreuid</tt> call failed for some reason in the setuid emulator
of <em class="emphasis">suidperl</em>.</p>
</dd>


<dt>
<b><tt class="literal">Can't take log of</tt> <em class="replaceable">%g</em></b>
</dt>
<dd>
<p>(F) For ordinary real numbers, you can't take the logarithm of a
negative number or zero. There's a <tt class="literal">Math::Complex</tt> package that comes
standard with Perl, though, if you really want to do that for
the negative numbers.</p>
</dd>


<dt>
<b><tt class="literal">Can't take sqrt of</tt> <em class="replaceable">%g</em></b>
</dt>
<dd>
<p>(F) For ordinary real numbers, you can't take the square root of a
negative number.  There's a <tt class="literal">Math::Complex</tt> package that comes standard
with Perl, though, if you really want to do that.</p>
</dd>


<dt>
<b><tt class="literal">Can't undef active subroutine</tt></b>
</dt>
<dd>
<p>(F) You can't undefine a routine that's currently running.  You can,
however, redefine it while it's running, and you can even <tt class="literal">undef</tt> the
redefined subroutine while the old routine is running.  Go figure.</p>
</dd>


<dt>
<b><tt class="literal">Can't unshift</tt></b>
</dt>
<dd>
<p>(F) You tried to unshift an "unreal" array that can't be <tt class="literal">unshift</tt>ed,
such as the main Perl stack.</p>
</dd>


<dt>
<b><tt class="literal">Can't upgrade that kind of scalar</tt></b>
</dt>
<dd>
<p>(P) The internal <tt class="literal">sv_upgrade</tt> routine adds "members" to an SV, making
it into a more specialized kind of SV.  The top several SV types are
so specialized, however, that they cannot be interconverted.  This
message indicates that such a conversion was attempted.</p>
</dd>


<dt>
<b><tt class="literal">Can't upgrade to undef</tt></b>
</dt>
<dd>
<p>(P) The undefined SV is the bottom of the totem pole, in the scheme
of upgradability.  Upgrading to <tt class="literal">undef</tt> indicates an error in the
code calling <tt class="literal">sv_upgrade</tt>.</p>
</dd>


<dt>
<b><tt class="literal">Can't use %%! because Errno.pm is not available</tt></b>
</dt>
<dd>
<p>(F) The first time the <tt class="literal">%!</tt> hash is used, Perl automatically loads
the <tt class="literal">Errno</tt> module. The <tt class="literal">Errno</tt> module is expected to tie the <tt class="literal">%!</tt>
hash to provide symbolic names for <tt class="literal">$!</tt> errno values.</p>
</dd>


<dt>
<b><tt class="literal">Can't use "my</tt> <em class="replaceable">%s</em><tt class="literal">" in sort comparison</tt></b>
</dt>
<dd>
<p>(F) The global variables <tt class="literal">$a</tt> and <tt class="literal">$b</tt> are reserved for sort
comparisons.  You mentioned <tt class="literal">$a</tt> or <tt class="literal">$b</tt> in the same line as the 
<tt class="literal">&lt;=&gt;</tt> or <tt class="literal">cmp</tt> operator, and the variable had earlier been declared
as a lexical variable.  Either qualify the sort variable with the
package name, or rename the lexical variable.</p>
</dd>


<dt>
<b><tt class="literal">Bad evalled substitution pattern</tt></b>
</dt>
<dd>
<p>(F) You've used the <tt class="literal">/e</tt> switch to evaluate the replacement for a
substitution, but Perl found a syntax error in the code to evaluate,
most likely an unexpected right brace <tt class="literal">}</tt>.</p>
</dd>


<dt>
<b><tt class="literal">Can't use</tt> <em class="replaceable">%s</em> <tt class="literal">for loop variable</t