path: root/pod/perldiag.pod

=head1 NAME

perldiag - various Perl diagnostics

=head1 DESCRIPTION

These messages are classified as follows (listed in increasing order of
desperation):

    (W) A warning (optional).
    (D) A deprecation (optional).
    (S) A severe warning (mandatory).
    (F) A fatal error (trappable).
    (P) An internal error you should never see (trappable).
    (X) A very fatal error (non-trappable).

Optional warnings are enabled by using the B<-w> switch.  Trappable
errors may be trapped using the eval operator.  See L<perlfunc/eval>.

Some of these messages are generic.  Spots that vary are denoted with a %s,
just as in a printf format.  Note that some message start with a %s!
The symbols C<"%-?@> sort before the letters, while C<[> and C<\> sort after.

=over 4

=item "my" variable %s can't be in a package

(F) Lexically scoped variables aren't in a package, so it doesn't make sense
to try to declare one with a package qualifier on the front.  Use local()
if you want to localize a package variable.

=item "no" not allowed in expression

(F) The "no" keyword is recognized and executed at compile time, and returns
no useful value.  See L<perlmod>.

=item "use" not allowed in expression

(F) The "use" keyword is recognized and executed at compile time, and returns
no useful value.  See L<perlmod>.

=item % may only be used in unpack

(F) You can't pack a string by supplying a checksum, since the
checksumming process loses information, and you can't go the other
way.  See L<perlfunc/unpack>.

=item %s (...) interpreted as function

(W) You've run afoul of the rule that says that any list operator followed
by parentheses turns into a function, with all the list operators arguments 
found inside the parens.  See L<perlop/Terms and List Operators (Leftward)>.

=item %s argument is not a HASH element

(F) The argument to delete() or exists() must be a hash element, such as

    $foo{$bar}
    $ref->[12]->{"susie"}

=item %s did not return a true value

(F) A required (or used) file must return a true value to indicate that
it compiled correctly and ran its initialization code correctly.  It's
traditional to end such a file with a "1;", though any true value would
do.  See L<perlfunc/require>.

=item %s found where operator expected

(S) The Perl lexer knows whether to expect a term or an operator.  If it
sees what it knows to be a term when it was expecting to see an operator,
it gives you this warning.  Usually it indicates that an operator or
delimiter was omitted, such as a semicolon.

=item %s had compilation errors.

(F) The final summary message when a C<perl -c> fails.

=item %s has too many errors.

(F) The parser has given up trying to parse the program after 10 errors.
Further error messages would likely be uninformative.

=item %s matches null string many times

(W) The pattern you've specified would be an infinite loop if the
regular expression engine didn't specifically check for that.  See L<perlre>.

=item %s never introduced

(S) The symbol in question was declared but somehow went out of scope
before it could possibly have been used.

=item %s syntax OK

(F) The final summary message when a C<perl -c> succeeds.

=item B<-P> not allowed for setuid/setgid script

(F) The script would have to be opened by the C preprocessor by name,
which provides a race condition that breaks security.

=item C<-T> and C<-B> not implemented on filehandles

(F) Perl can't peek at the stdio buffer of filehandles when it doesn't
know about your kind of stdio.  You'll have to use a filename instead.

=item ?+* follows nothing in regexp

(F) You started a regular expression with a quantifier.  Backslash it
if you meant it literally.   See L<perlre>.

=item @ outside of string

(F) You had a pack template that specified an absolution position outside
the string being unpacked.  See L<perlfunc/pack>.

=item accept() on closed fd

(W) You tried to do an accept on a closed socket.  Did you forget to check
the return value of your socket() call?  See L<perlfunc/accept>.

=item Allocation too large: %lx

(F) You can't allocate more than 64K on an MSDOS machine.

=item Arg too short for msgsnd

(F) msgsnd() requires a string at least as long as sizeof(long).

=item Args must match #! line

(F) The setuid emulator requires that the arguments Perl was invoked
with match the arguments specified on the #! line.

=item Argument "%s" isn't numeric

(W) The indicated string was fed as an argument to an operator that
expected a numeric value instead.  If you're fortunate the message
will identify which operator was so unfortunate.

=item Array @%s missing the @ in argument %d of %s()

(D) Really old Perl let you omit the @ on array names in some spots.  This
is now heavily deprecated.

=item assertion botched: %s

(P) The malloc package that comes with Perl had an internal failure.

=item Assertion failed: file "%s"

(P) A general assertion failed.  The file in question must be examined.

=item Assignment to both a list and a scalar

(F) If you assign to a conditional operator, the 2nd and 3rd arguments
must either both be scalars or both be lists.  Otherwise Perl won't
know which context to supply to the right side.

=item Attempt to free non-arena SV: 0x%lx

(P) All SV objects are supposed to be allocated from arenas that will
be garbage collected on exit.  An SV was discovered to be outside any
of those arenas.

=item Attempt to free temp prematurely

(W) Mortalized values are supposed to be freed by the free_tmps()
routine.  This indicates that something else is freeing the SV before
the free_tmps() routine gets a chance, which means that the free_tmps()
routine will be freeing an unreferenced scalar when it does try to free
it.

=item Attempt to free unreferenced glob pointers

(P) The reference counts got screwed up on symbol aliases.

=item Attempt to free unreferenced scalar

(W) Perl went to decrement the reference count of a scalar to see if it
would go to 0, and discovered that it had already gone to 0 earlier,
and should have been freed, and in fact, probably was freed.  This
could indicate that SvREFCNT_dec() was called too many times, or that
SvREFCNT_inc() was called too few times, or that the SV was mortalized
when it shouldn't have been, or that memory has been corrupted.

=item Bad arg length for %s, is %d, should be %d

(F) You passed a buffer of the wrong size to one of msgctl(), semctl() or
shmctl().  In C parlance, the correct sized are, respectively,
S<sizeof(struct msqid_ds *)>, S<sizeof(struct semid_ds *)> and
S<sizeof(struct shmid_ds *)>.

=item Bad associative array

(P) One of the internal hash routines was passed a null HV pointer.

=item Bad filehandle: %s

(F) A symbol was passed to something wanting a filehandle, but the symbol
has no filehandle associated with it.  Perhaps you didn't do an open(), or
did it in another package.

=item Bad free() ignored

(S) An internal routine called free() on something that had never been
malloc()ed in the first place.

=item Bad name after %s::

(F) You started to name a symbol by using a package prefix, and then didn't
finish the symbol.  In particular, you can't interpolate outside of quotes,
so

    $var = 'myvar';
    $sym = mypack::$var;

is not the same as

    $var = 'myvar';
    $sym = "mypack::$var";

=item Bad symbol for array

(P) An internal request asked to add an array entry to something that
wasn't a symbol table entry.

=item Bad symbol for filehandle

(P) An internal request asked to add a filehandle entry to something that
wasn't a symbol table entry.

=item Bad symbol for hash

(P) An internal request asked to add a hash entry to something that
wasn't a symbol table entry.

=item BEGIN failed--compilation aborted

(F) An untrapped exception was raised while executing a BEGIN subroutine.
Compilation stops immediately and the interpreter is exited.

=item bind() on closed fd

(W) You tried to do a bind on a closed socket.  Did you forget to check
the return value of your socket() call?  See L<perlfunc/bind>.

=item Callback called exit

(F) A subroutine invoked from an external package via perl_call_sv()
exited by calling exit.

=item Can't "last" outside a block

(F) A "last" statement was executed to break out of the current block,
except that there's this itty bitty problem called there isn't a
current block.  Note that an "if" or "else" block doesn't count as a
"loopish" block.  You can usually double the curlies to get the same
effect though, since the inner curlies will be considered a block
that loops once.  See L<perlfunc/last>.

=item Can't "next" outside a block

(F) A "next" statement was executed to reiterate the current block, but
there isn't a current block.  Note that an "if" or "else" block doesn't
count as a "loopish" block.  You can usually double the curlies to get
the same effect though, since the inner curlies will be considered a block
that loops once.  See L<perlfunc/last>.

=item Can't "redo" outside a block

(F) A "redo" statement was executed to restart the current block, but
there isn't a current block.  Note that an "if" or "else" block doesn't
count as a "loopish" block.  You can usually double the curlies to get
the same effect though, since the inner curlies will be considered a block
that loops once.  See L<perlfunc/last>.

=item Can't bless non-reference value

(F) Only hard references may be blessed.  This is how Perl "enforces"
encapsulation of objects.  See L<perlobj>.

=item Can't break at that line

(S) A warning intended for while running within the debugger, indicating
the line number specified wasn't the location of a statement that could
be stopped at.

=item Can't call method "%s" in empty package "%s"

(F) You called a method correctly, and it correctly indicated a package
functioning as a class, but that package doesn't have ANYTHING defined
in it, let alone methods.  See L<perlobj>.

=item Can't call method "%s" on unblessed reference

(F) A method call must know what package it's supposed to run in.  It
ordinarily finds this out from the object reference you supply, but
you didn't supply an object reference in this case.  A reference isn't
an object reference until it has been blessed.  See L<perlobj>.

=item Can't call method "%s" without a package or object reference

(F) You used the syntax of a method call, but the slot filled by the
object reference or package name contains an expression that returns
neither an object reference nor a package name.  (Perhaps it's null?)
Something like this will reproduce the error:

    $BADREF = undef;
    process $BADREF 1,2,3;
    $BADREF->process(1,2,3);

=item Can't chdir to %s

(F) You called C<perl -x/foo/bar>, but C</foo/bar> is not a directory
that you can chdir to, possibly because it doesn't exist.

=item Can't coerce %s to integer in %s

(F) Certain types of SVs, in particular real symbol table entries
(type GLOB), can't be forced to stop being what they are.  So you can't
say things like:

    *foo += 1;

You CAN say

    $foo = *foo;
    $foo += 1;

but then $foo no longer contains a glob.

=item Can't coerce %s to number in %s

(F) Certain types of SVs, in particular real symbol table entries
(type GLOB), can't be forced to stop being what they are.

=item Can't coerce %s to string in %s

(F) Certain types of SVs, in particular real symbol table entries
(type GLOB), can't be forced to stop being what they are.

=item Can't create pipe mailbox

(F) An error peculiar to VMS.

=item Can't declare %s in my

(F) Only scalar, array and hash variables may be declared as lexical variables.
They must have ordinary identifiers as names.

=item Can't do inplace edit on %s: %s

(S) The creation of the new file failed for the indicated reason.

=item Can't do inplace edit without backup

(F) You're on a system such as MSDOS that gets confused if you try reading
from a deleted (but still opened) file.  You have to say B<-i>C<.bak>, or some
such.

=item Can't do inplace edit: %s > 14 characters

(S) There isn't enough room in the filename to make a backup name for the file.

=item Can't do inplace edit: %s is not a regular file

(S) You tried to use the B<-i> switch on a special file, such as a file in
/dev, or a FIFO.  The file was ignored.

=item Can't do setegid!

(P) The setegid() call failed for some reason in the setuid emulator
of suidperl.

=item Can't do seteuid!

(P) The setuid emulator of suidperl failed for some reason.

=item Can't do setuid

(F) This typically means that ordinary perl tried to exec suidperl to
do setuid emulation, but couldn't exec it.  It looks for a name of the
form sperl5.000 in the same directory that the perl executable resides
under the name perl5.000, typically /usr/local/bin on Unix machines.
If the file is there, check the execute permissions.  If it isn't, ask
your sysadmin why he and/or she removed it.

=item Can't do waitpid with flags

(F) This machine doesn't have either waitpid() or wait4(), so only waitpid()
without flags is emulated.

=item Can't do {n,m} with n > m

(F) Minima must be less than or equal to maxima.  If you really want
your regexp to match something 0 times, just put {0}.  See L<perlre>.

=item Can't emulate -%s on #! line

(F) The #! line specifies a switch that doesn't make sense at this point.
For example, it'd be kind of silly to put a B<-x> on the #! line.

=item Can't exec "%s": %s

(W) An system(), exec() or piped open call could not execute the named
program for the indicated reason.  Typical reasons include: the permissions
were wrong on the file, the file wasn't found in C<$ENV{PATH}>, the
executable in question was compiled for another architecture, or the
#! line in a script points to an interpreter that can't be run for
similar reasons.  (Or maybe your system doesn't support #! at all.)

=item Can't exec %s

(F) Perl was trying to execute the indicated program for you because that's
what the #! line said.  If that's not what you wanted, you may need to
mention "perl" on the #! line somewhere.

=item Can't execute %s

(F) You used the B<-S> switch, but the script to execute could not be found
in the PATH, or at least not with the correct permissions.

=item Can't find label %s

(F) You said to goto a label that isn't mentioned anywhere that it's possible
for us to go to.  See L<perlfunc/goto>.

=item Can't find string terminator %s anywhere before EOF

(F) Perl strings can stretch over multiple lines.  This message means that
the closing delimiter was omitted.  Since bracketed quotes count nesting
levels, the following is missing its final parenthesis:

    print q(The character '(' starts a side comment.)

=item Can't fork

(F) A fatal error occurred while trying to fork while opening a pipeline.

=item Can't get pipe mailbox device name

(F) An error peculiar to VMS.

=item Can't get SYSGEN parameter value for MAXBUF

(F) An error peculiar to VMS.

=item Can't goto subroutine outside a subroutine

(F) The deeply magical "goto subroutine" call can only replace one subroutine
call for another.  It can't manufacture one out of whole cloth.  In general
you should only be calling it out of an AUTOLOAD routine anyway.  See
L<perlfunc/goto>.

=item Can't locate %s in @INC

(F) You said to do (or require, or use) a file that couldn't be found
in any of the libraries mentioned in @INC.  Perhaps you need to set
the PERL5LIB environment variable to say where the extra library is,
or maybe the script needs to add the library name to @INC.  Or maybe
you just misspelled the name of the file.  See L<perlfunc/require>.

=item Can't locate object method "%s" via package "%s"

(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 it's base classes.  See L<perlobj>.

=item Can't locate package %s for @%s::ISA

(W) The @ISA array contained the name of another package that doesn't seem
to exist.

=item Can't mktemp()

(F) The mktemp() routine failed for some reason while trying to process
a B<-e> switch.  Maybe your /tmp partition is full, or clobbered.

=item Can't modify %s in %s

(F) You aren't allowed to assign to the item indicated, or otherwise try to
change it, such as with an autoincrement.

=item Can't modify non-existent substring

(P) The internal routine that does assignment to a substr() was handed
a NULL.

=item Can't msgrcv to readonly var

(F) The target of a msgrcv must be modifiable in order to be used as a receive
buffer.

=item Can't open %s: %s

(S) An inplace edit couldn't open the original file for the indicated reason.
Usually this is because you don't have read permission for the file.

=item Can't open bidirectional pipe

(W) You tried to say C<open(CMD, "|cmd|")>, which is not supported.  You can
try any of several modules in the Perl library to do this, such as
"open2.pl".  Alternately, direct the pipe's output to a file using ">",
and then read it in under a different file handle.

=item Can't open perl script "%s": %s

(F) The script you specified can't be opened for the indicated reason.

=item Can't rename %s to %s: %s, skipping file

(S) The rename done by the B<-i> switch failed for some reason, probably because
you don't have write permission to the directory.

=item Can't reswap uid and euid

(P) The setreuid() call failed for some reason in the setuid emulator
of suidperl.

=item Can't return outside a subroutine

(F) The return statement was executed in mainline code, that is, where
there was no subroutine call to return out of.  See L<perlsub>.

=item Can't stat script "%s"

(P) For some reason you can't fstat() the script even though you have
it open already.  Bizarre.

=item Can't swap uid and euid

(P) The setreuid() call failed for some reason in the setuid emulator
of suidperl.

=item Can't take log of %g

(F) Logarithms are only defined on positive real numbers.

=item Can't take sqrt of %g

(F) For ordinary real numbers, you can't take the square root of a
negative number.  There's a Complex package available for Perl, though,
if you really want to do that.

=item Can't undef active subroutine

(F) You can't undefine a routine that's currently running.  You can,
however, redefine it while it's running, and you can even undef the
redefined subroutine while the old routine is running.  Go figure.

=item Can't unshift

(F) You tried to unshift an "unreal" array that can't be unshifted, such
as the main Perl stack.

=item Can't upgrade that kind of scalar

(P) The internal sv_upgrade 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.

=item Can't upgrade to undef

(P) The undefined SV is the bottom of the totem pole, in the scheme
of upgradability.  Upgrading to undef indicates an error in the
code calling sv_upgrade.

=item Can't use %s as left arg of an implicit ->

(F) The compiler tried to interpret a bracketed expression as a subscript
to an array reference.  But to the left of the brackets was an expression
that didn't end in an arrow (->), or look like a subscripted expression.
Only subscripted expressions with multiple subscripts are allowed to omit 
the intervening arrow.

=item Can't use %s for loop variable

(F) Only a simple scalar variable may be used as a loop variable on a foreach.

=item Can't use %s ref as %s ref

(F) You've mixed up your reference types.  You have to dereference a
reference of the type needed.  You can use the ref() function to
test the type of the reference, if need be.

=item Can't use a string as %s ref while "strict refs" in use

(F) Only hard references are allowed by "strict refs".  Symbolic references
are disallowed.  See L<perlref>.

=item Can't use an undefined value as %s reference

(F) A value used as either a hard reference or a symbolic reference must
be a defined value.  This helps to de-lurk some insidious errors.

=item Can't use delimiter brackets within expression

(F) The ${name} construct is for disambiguating identifiers in strings, not
in ordinary code.

=item Can't use global %s in "my"

(F) You tried to declare a magical variable as a lexical variable.  This is
not allowed, because the magic can only be tied to one location (namely
the global variable) and it would be incredibly confusing to have
variables in your program that looked like magical variables but
weren't.

=item Can't write to temp file for B<-e>: %s

(F) The write routine failed for some reason while trying to process
a B<-e> switch.  Maybe your /tmp partition is full, or clobbered.

=item Can't x= to readonly value

(F) You tried to repeat a constant value (often the undefined value) with
an assignment operator, which implies modifying the value itself.
Perhaps you need to copy the value to a temporary, and repeat that.

=item Cannot open temporary file

(F) The create routine failed for some reaon while trying to process
a B<-e> switch.  Maybe your /tmp partition is full, or clobbered.

=item chmod: mode argument is missing initial 0

(W) A novice will sometimes say

    chmod 777, $filename

not realizing that 777 will be interpreted as a decimal number, equivalent
to 01411.  Octal constants are introduced with a leading 0 in Perl, as in C.

=item Close on unopened file <%s>

(W) You tried to close a filehandle that was never opened.

=item connect() on closed fd

(W) You tried to do a connect on a closed socket.  Did you forget to check
the return value of your socket() call?  See L<perlfunc/connect>.

=item Corrupt malloc ptr 0x%lx at 0x%lx

(P) The malloc package that comes with Perl had an internal failure.

=item corrupted regexp pointers

(P) The regular expression engine got confused by what the regular
expression compiler gave it.

=item corrupted regexp program

(P) The regular expression engine got passed a regexp program without
a valid magic number.

=item Deep recursion on subroutine "%s"

(W) This subroutine has called itself (directly or indirectly) 100
times than it has returned.  This probably indicates an infinite
recursion, unless you're writing strange benchmark programs, in which
case it indicates something else.

=item Did you mean $ instead of %?

(W) You probably said %hash{$key} when you meant $hash{$key}.

=item Don't know how to handle magic of type '%s'

(P) The internal handling of magical variables has been cursed.

=item do_study: out of memory

(P) This should have been caught by safemalloc() instead.

=item Duplicate free() ignored

(S) An internal routine called free() on something that had already
been freed.

=item END failed--cleanup aborted

(F) An untrapped exception was raised while executing an END subroutine.
The interpreter is immediately exited.

=item Execution of %s aborted due to compilation errors.

(F) The final summary message when a Perl compilation fails.

=item Exiting eval via %s

(W) You are exiting an eval by unconventional means, such as a
a goto, or a loop control statement.

=item Exiting subroutine via %s

(W) You are exiting a subroutine by unconventional means, such as a
a goto, or a loop control statement.

=item Exiting substitution via %s

(W) You are exiting a substitution by unconventional means, such as a
a return, a goto, or a loop control statement.

=item Fatal $PUTMSG error: %d

(F) An error peculiar to VMS.

=item fcntl is not implemented

(F) Your machine apparently doesn't implement fcntl().  What is this, a
PDP-11 or something?

=item Filehandle %s never opened

(W) An I/O operation was attempted on a filehandle that was never initialized.
You need to do an open() or a socket() call, or call a constructor from
the FileHandle package.

=item Filehandle %s opened only for input

(W) You tried to write on a read-only filehandle.  If you
intended it to be a read-write filehandle, you needed to open it with
"+<" or "+>" or "+>>" instead of with "<" or nothing.  If you only
intended to write the file, use ">" or ">>".  See L<perlfunc/open>.

=item Filehandle only opened for input

(W) You tried to write on a read-only filehandle.  If you
intended it to be a read-write filehandle, you needed to open it with
"+<" or "+>" or "+>>" instead of with "<" or nothing.  If you only
intended to write the file, use ">" or ">>".  See L<perlfunc/open>.

=item Final $ should be \$ or $name

(F) You must now decide whether the final $ in a string was meant to be
a literal dollar sign, or was meant to introduce a variable name
that happens to be missing.  So you have to put either the backslash or
the name.

=item Final @ should be \@ or @name

(F) You must now decide whether the final @ in a string was meant to be
a literal "at" sign, or was meant to introduce a variable name
that happens to be missing.  So you have to put either the backslash or
the name.

=item Format %s redefined

(W) You redefined a format.  To suppress this warning, say

    {
	local $^W = 0;
	eval "format NAME =...";
    }

=item Format not terminated

(F) A format must be terminated by a line with a solitary dot.  Perl got
to the end of your file without finding such a line.

=item Found = in conditional, should be ==

(W) You said

    if ($foo = 123)

when you meant

    if ($foo == 123)

(or something like that).

=item gdbm store returned %d, errno %d, key "%s"

(S) A warning from the GDBM_File extension that a store failed.

=item gethostent not implemented

(F) Your C library apparently doesn't implement gethostent(), probably
because if it did, it'd feel morally obligated to return every hostname
on the Internet.

=item get{sock,peer}name() on closed fd

(W) You tried to get a socket or peer socket name on a closed socket.
Did you forget to check the return value of your socket() call?

=item Glob not terminated

(F) The lexer saw a left angle bracket in a place where it was expecting
a term, so it's looking for the corresponding right angle bracket, and not
finding it.  Chances are you left some needed parentheses out earlier in
the line, and you really meant a "less than".

=item Global symbol "%s" requires explicit package name

(F) You've said "use strict vars", which indicates that all variables must
either be lexically scoped (using "my"), or explicitly qualified to
say which package the global variable is in (using "::").

=item goto must have label

(F) Unlike with "next" or "last", you're not allowed to goto an
unspecified destination.  See L<perlfunc/goto>.

=item Had to create %s unexpectedly

(S) A routine asked for a symbol from a symbol table that ought to have
existed already, but for some reason it didn't, and had to be created on
an emergency basis to prevent a core dump.

=item Hash %%s missing the % in argument %d of %s()

(D) Really old Perl let you omit the % on hash names in some spots.  This
is now heavily deprecated.

=item Identifier "%s::%s" used only once: possible typo

(W) Typographical errors often show up as unique identifiers.  If you
had a good reason for having a unique identifier, then just mention it
again somehow to suppress the message.

=item Illegal division by zero

(F) You tried to divide a number by 0.  Either something was wrong in your
logic, or you need to put a conditional in to guard against meaningless input.

=item Illegal modulus zero

(F) You tried to divide a number by 0 to get the remainder.  Most numbers
don't take to this kindly.

=item Illegal octal digit

(F) You used an 8 or 9 in a octal number.

=item Insecure dependency in %s

(F) You tried to do something that the tainting mechanism didn't like. 
The tainting mechanism is turned on when you're running setuid or setgid,
or when you specify B<-T> to turn it on explicitly.  The tainting mechanism
labels all data that's derived directly or indirectly from the user,
who is considered to be unworthy of your trust.  If any such data is
used in a "dangerous" operation, you get this error.  See L<perlsec>
for more information.

=item Insecure directory in %s

(F) You can't use system(), exec(), or a piped open in a setuid or setgid
script if $ENV{PATH} contains a directory that is writable by the world.
See L<perlsec>.

=item Insecure PATH

(F) You can't use system(), exec(), or a piped open in a setuid or
setgid script if $ENV{PATH} is derived from data supplied (or
potentially supplied) by the user.  The script must set the path to a
known value, using trustworthy data.  See L<perlsec>.

=item internal disaster in regexp

(P) Something went badly wrong in the regular expression parser.

=item internal urp in regexp at /%s/

(P) Something went badly awry in the regular expression parser.

=item invalid [] range in regexp

(F) The range specified in a character class had a minimum character
greater than the maximum character.  See L<perlre>.

=item ioctl is not implemented

(F) Your machine apparently doesn't implement ioctl(), which is pretty
strange for a machine that supports C.

=item junk on end of regexp

(P) The regular expression parser is confused.

=item Label not found for "last %s"

(F) You named a loop to break out of, but you're not currently in a
loop of that name, not even if you count where you were called from.
See L<perlfunc/last>.

=item Label not found for "next %s"

(F) You named a loop to continue, but you're not currently in a loop of
that name, not even if you count where you were called from.  See
L<perlfunc/last>.

=item Label not found for "redo %s"

(F) You named a loop to restart, but you're not currently in a loop of
that name, not even if you count where you were called from.  See
L<perlfunc/last>.

=item listen() on closed fd

(W) You tried to do a listen on a closed socket.  Did you forget to check
the return value of your socket() call?  See L<perlfunc/listen>.

=item Literal @%s now requires backslash

(F) It used to be that Perl would try to guess whether you wanted an
array interpolated or a literal @.  It did this when the string was
first used at runtime.  Now strings are parsed at compile time, and
ambiguous instances of @ must be disambiguated, either by putting a
backslash to indicate a literal, or by declaring (or using) the array
within the program before the string (lexically).  (Someday it will simply
assume that an unbackslashed @ interpolates an array.)

=item Method for operation %s not found in package %s during blessing

(F) An attempt was made to specify an entry in an overloading table that
doesn't somehow point to a valid method.  See L<perlovl>.

=item Might be a runaway multi-line %s string starting on line %d

(S) An advisory indicating that the previous error may have been caused
by a missing delimiter on a string or pattern, because it eventually
ended earlier on the current line.

=item Misplaced _ in number

(W) An underline in a decimal constant wasn't on a 3-digit boundary.

=item Missing $ on loop variable

(F) Apparently you've been programming in csh too much.  Variables are always
mentioned with the $ in Perl, unlike in the shells, where it can vary from 
one line to the next.

=item Missing comma after first argument to %s function

(F) While certain functions allow you to specify a filehandle or an
"indirect object" before the argument list, this ain't one of them.

=item Missing right bracket

(F) The lexer counted more opening curly brackets (braces) than closing ones.
As a general rule, you'll find it's missing near the place you were last
editing.

=item Missing semicolon on previous line?

(S) This is an educated guess made in conjunction with the message "%s
found where operator expected".  Don't automatically put a semicolon on
the previous line just because you saw this message.

=item Modification of a read-only value attempted

(F) You tried, directly or indirectly, to change the value of a
constant.  You didn't, of course, try "2 = 1", since the compiler
catches that.  But an easy way to do the same thing is:

    sub mod { $_[0] = 1 }
    mod(2);

Another way is to assign to a substr() that's off the end of the string.

=item Modification of non-creatable array value attempted, subscript %d

(F) You tried to make an array value spring into existence, and the
subscript was probably negative, even counting from end of the array
backwards.

=item Modification of non-creatable hash value attempted, subscript "%s"

(F) You tried to make a hash value spring into existence, and it couldn't
be created for some peculiar reason.

=item Module name must be constant

(F) Only a bare module name is allowed as the first argument to a "use".

=item msg%s not implemented

(F) You don't have System V message IPC on your system.

=item Multidimensional syntax %s not supported

(W) Multidimensional arrays aren't written like $foo[1,2,3].  They're written
like $foo[1][2][3], as in C.

=item Negative length

(F) You tried to do a read/write/send/recv operation with a buffer length
that is less than 0.  This is difficult to imagine.

=item nested *?+ in regexp

(F) You can't quantify a quantifier without intervening parens.  So
things like ** or +* or ?* are illegal.

Note, however, that the minimal matching quantifiers, *?, +? and ?? appear
to be nested quantifiers, but aren't.  See L<perlre>.

=item No #! line

(F) The setuid emulator requires that scripts have a well-formed #! line
even on machines that don't support the #! construct.

=item No %s allowed while running setuid

(F) Certain operations are deemed to be too insecure for a setuid or setgid
script to even be allowed to attempt.  Generally speaking there will be
another way to do what you want that is, if not secure, at least securable.
See L<perlsec>.

=item No B<-e> allowed in setuid scripts

(F) A setuid script can't be specified by the user.

=item No comma allowed after %s

(F) A list operator that has a filehandle or "indirect object" is not
allowed to have a comma between that and the following arguments.
Otherwise it'd be just another one of the arguments.

=item No DB::DB routine defined

(F) The currently executing code was compiled with the B<-d> switch,
but for some reason the perl5db.pl file (or some facsimile thereof)
didn't define a routine to be called at the beginning of each
statement.  Which is odd, because the file should have been required
automatically, and should have blown up the require if it didn't parse
right.

=item No dbm on this machine

(P) This is counted as an internal error, because every machine should
supply dbm nowadays, since Perl comes with SDBM.  See L<SDBM_File>.

=item No DBsub routine

(F) The currently executing code was compiled with the B<-d> switch,
but for some reason the perl5db.pl file (or some facsimile thereof)
didn't define a DB::sub routine to be called at the beginning of each
ordinary subroutine call.

=item No Perl script found in input

(F) You called C<perl -x>, but no line was found in the file beginning
with #! and containing the word "perl".

=item No setregid available

(F) Configure didn't find anything resembling the setregid() call for
your system.

=item No setreuid available

(F) Configure didn't find anything resembling the setreuid() call for
your system.

=item No space allowed after B<-I>

(F) The argument to B<-I> must follow the B<-I> immediately with no
intervening space.

=item No such signal: SIG%s

(W) You specified a signal name as a subscript to %SIG that was not recognized.
Say C<kill -l> in your shell to see the valid signal names on your system.

=item Not a CODE reference

(F) Perl was trying to evaluate a reference to a code value (that is, a
subroutine), but found a reference to something else instead.  You can
use the ref() function to find out what kind of ref it really was.
See also L<perlref>.

=item Not a format reference

(F) I'm not sure how you managed to generate a reference to an anonymous
format, but this indicates you did, and that it didn't exist.

=item Not a GLOB reference

(F) Perl was trying to evaluate a reference to a "type glob" (that is,
a symbol table entry that looks like C<*foo>), but found a reference to
something else instead.  You can use the ref() function to find out
what kind of ref it really was.  See L<perlref>.

=item Not a HASH reference

(F) Perl was trying to evaluate a reference to a hash value, but
found a reference to something else instead.  You can use the ref()
function to find out what kind of ref it really was.  See L<perlref>.

=item Not a perl script

(F) The setuid emulator requires that scripts have a well-formed #! line
even on machines that don't support the #! construct.  The line must
mention perl.

=item Not a SCALAR reference

(F) Perl was trying to evaluate a reference to a scalar value, but
found a reference to something else instead.  You can use the ref()
function to find out what kind of ref it really was.  See L<perlref>.

=item Not a subroutine reference

(F) Perl was trying to evaluate a reference to a code value (that is, a
subroutine), but found a reference to something else instead.  You can
use the ref() function to find out what kind of ref it really was.
See also L<perlref>.

=item Not a subroutine reference in %OVERLOAD

(F) An attempt was made to specify an entry in an overloading table that
doesn't somehow point to a valid subroutine.  See L<perlovl>.

=item Not an ARRAY reference

(F) Perl was trying to evaluate a reference to an array value, but
found a reference to something else instead.  You can use the ref()
function to find out what kind of ref it really was.  See L<perlref>.

=item Not enough arguments for %s

(F) The function requires more arguments than you specified.

=item Not enough format arguments

(W) A format specified more picture fields than the next line supplied.
See L<perlform>.

=item Null filename used

(F) You can't require the null filename, especially since on many machines
that means the current directory!  See L<perlfunc/require>.

=item NULL OP IN RUN

(P) Some internal routine called run() with a null opcode pointer.

=item Null realloc

(P) An attempt was made to realloc NULL.

=item NULL regexp argument

(P) The internal pattern matching routines blew it bigtime.

=item NULL regexp parameter

(P) The internal pattern matching routines are out of their gourd.

=item Odd number of elements in hash list

(S) You specified an odd number of elements to a hash list, which is odd,
since hash lists come in key/value pairs.

=item oops: oopsAV

(S) An internal warning that the grammar is screwed up.

=item oops: oopsHV

(S) An internal warning that the grammar is screwed up.

=item Operation `%s' %s: no method found,

(F) An attempt was made to use an entry in an overloading table that
somehow no longer points to a valid method.  See L<perlovl>.

=item Out of memory for yacc stack

(F) The yacc parser wanted to grow its stack so it could continue parsing,
but realloc() wouldn't give it more memory, virtual or otherwise.

=item Out of memory!

(X) The malloc() function returned 0, indicating there was insufficient
remaining memory (or virtual memory) to satisfy the request.

=item page overflow

(W) A single call to write() produced more lines than can fit on a page.
See L<perlform>.

=item panic: ck_grep

(P) Failed an internal consistency check trying to compile a grep.

=item panic: ck_split

(P) Failed an internal consistency check trying to compile a split.

=item panic: corrupt saved stack index

(P) The savestack was requested to restore more localized values than there
are in the savestack.

=item panic: die %s

(P) We popped the context stack to an eval context, and then discovered
it wasn't an eval context.

=item panic: do_match

(P) The internal pp_match() routine was called with invalid operational data.

=item panic: do_split

(P) Something terrible went wrong in setting up for the split.

=item panic: do_subst

(P) The internal pp_subst() routine was called with invalid operational data.

=item panic: do_trans

(P) The internal do_trans() routine was called with invalid operational data.

=item panic: goto

(P) We popped the context stack to a context with the specified label,
and then discovered it wasn't a context we know how to do a goto in.

=item panic: INTERPCASEMOD

(P) The lexer got into a bad state at a case modifier.

=item panic: INTERPCONCAT

(P) The lexer got into a bad state parsing a string with brackets.

=item panic: last

(P) We popped the context stack to a block context, and then discovered
it wasn't a block context.

=item panic: leave_scope clearsv

(P) A writable lexical variable became readonly somehow within the scope.

=item panic: leave_scope inconsistency

(P) The savestack probably got out of sync.  At least, there was an
invalid enum on the top of it.

=item panic: malloc

(P) Something requested a negative number of bytes of malloc.

=item panic: mapstart

(P) The compiler is screwed up with respect to the map() function.

=item panic: null array

(P) One of the internal array routines was passed a null AV pointer.

=item panic: pad_alloc

(P) The compiler got confused about which scratch pad it was allocating
and freeing temporaries and lexicals from.

=item panic: pad_free curpad

(P) The compiler got confused about which scratch pad it was allocating
and freeing temporaries and lexicals from.

=item panic: pad_free po

(P) An invalid scratch pad offset was detected internally.

=item panic: pad_reset curpad

(P) The compiler got confused about which scratch pad it was allocating
and freeing temporaries and lexicals from.

=item panic: pad_sv po

(P) An invalid scratch pad offset was detected internally.

=item panic: pad_swipe curpad

(P) The compiler got confused about which scratch pad it was allocating
and freeing temporaries and lexicals from.

=item panic: pad_swipe po

(P) An invalid scratch pad offset was detected internally.

=item panic: pp_iter

(P) The foreach iterator got called in a non-loop context frame.

=item panic: realloc

(P) Something requested a negative number of bytes of realloc.

=item panic: restartop

(P) Some internal routine requested a goto (or something like it), and
didn't supply the destination.

=item panic: return

(P) We popped the context stack to a subroutine or eval context, and
then discovered it wasn't a subroutine or eval context.

=item panic: scan_num

(P) scan_num() got called on something that wasn't a number.

=item panic: sv_insert

(P) The sv_insert() routine was told to remove more string than there
was string.

=item panic: top_env

(P) The compiler attempted to do a goto, or something weird like that.

=item panic: yylex

(P) The lexer got into a bad state while processing a case modifier.

=item Parens missing around "%s" list

(W) You said something like

    my $foo, $bar = @_;

when you meant

    my ($foo, $bar) = @_;

Remember that "my" and "local" bind closer than comma.

=item Perl %3.3f required--this is only version %s, stopped

(F) The module in question uses features of a version of Perl more recent
than the currently running version.  How long has it been since you upgraded,
anyway?  See L<perlfunc/require>.

=item Permission denied

(F) The setuid emulator in suidperl decided you were up to no good.

=item POSIX getpgrp can't take an argument

(F) Your C compiler uses POSIX getpgrp(), which takes no argument, unlike
the BSD version, which takes a pid.

=item Possible memory corruption: %s overflowed 3rd argument

(F) An ioctl() or fcntl() returned more than Perl was bargaining for.
Perl guesses a reasonable buffer size, but puts a sentinel byte at the
end of the buffer just in case.  This sentinel byte got clobbered, and
Perl assumes that memory is now corrupted.  See L<perlfunc/ioctl>.

=item Precedence problem: open %s should be open(%s)

(S) The old irregular construct
    
    open FOO || die;

is now misinterpreted as

    open(FOO || die);

because of the strict regularization of Perl 5's grammar into unary and
list operators.  (The old open was a little of both.) You must put
parens around the filehandle, or use the new "or" operator instead of "||".

=item print on closed filehandle %s

(W) The filehandle you're printing on got itself closed sometime before now.
Check your logic flow.

=item printf on closed filehandle %s

(W) The filehandle you're writing to got itself closed sometime before now.
Check your logic flow.

=item Probable precedence problem on %s

(W) The compiler found a bare word where it expected a conditional,
which often indicates that an || or && was parsed as part of the
last argument of the previous construct, for example:

    open FOO || die;

=item Read on closed filehandle <%s>

(W) The filehandle you're reading from got itself closed sometime before now.
Check your logic flow.

=item Reallocation too large: %lx

(F) You can't allocate more than 64K on an MSDOS machine.

=item Recompile perl with B<-D>DEBUGGING to use B<-D> switch

(F) You can't use the B<-D> option unless the code to produce the
desired output is compiled into Perl, which entails some overhead,
which is why it's currently left out of your copy.

=item Recursive inheritance detected

(F) More than 100 levels of inheritance were used.  Probably indicates
an unintended loop in your inheritance hierarchy.

=item Reference miscount in sv_replace()

(W) The internal sv_replace() function was handed a new SV with a
reference count of other than 1.

=item regexp memory corruption

(P) The regular expression engine got confused by what the regular
expression compiler gave it.

=item regexp out of space

(P) A "can't happen" error, because safemalloc() should have caught it earlier.

=item regexp too big

(F) The current implementation of regular expression uses shorts as
address offsets within a string.  Unfortunately this means that if
the regular expression compiles to longer than 32767, it'll blow up.
Usually when you want a regular expression this big, there is a better
way to do it with multiple statements.  See L<perlre>.

=item Reversed %s= operator

(W) You wrote your assignment operator backwards.  The = must always
comes last, to avoid ambiguity with subsequent unary operators.

=item Runaway format

(F) Your format contained the ~~ repeat-until-blank sequence, but it
produced 200 lines at once, and the 200th line looked exactly like the
199th line.  Apparently you didn't arrange for the arguments to exhaust
themselves, either by using ^ instead of @ (for scalar variables), or by
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
an array.  Generally it's better to ask for a scalar value (indicated by $).
The difference is that $foo[&bar] always behaves like a scalar, both when
assigning to it and when evaluating its argument, while @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 only expecting one subscript.

=item Script is not setuid/setgid in suidperl

(F) Oddly, the suidperl program was invoked on a script with its setuid
or setgid bit set.  This doesn't make much sense.

=item Search pattern not terminated

(F) The lexer couldn't find the final delimiter of a // or m{}
construct.  Remember that bracketing delimiters count nesting level.

=item seek() on unopened file

(W) You tried to use the seek() function on a filehandle that was either
never opened or has been closed since.

=item select not implemented

(F) This machine doesn't implement the select() system call.

=item sem%s not implemented

(F) You don't have System V semaphore IPC on your system.

=item semi-panic: attempt to dup freed string

(S) The internal newSVsv() routine was called to duplicate a scalar
that had previously been marked as free.

=item Semicolon seems to be missing

(W) A nearby syntax error was probably caused by a missing semicolon,
or possibly some other missing operator, such as a comma.

=item Send on closed socket

(W) The filehandle you're sending to got itself closed sometime before now.
Check your logic flow.

=item Sequence (?#... not terminated

(F) A regular expression comment must be terminated by a closing
parenthesis.  Embedded parens aren't allowed.  See L<perlre>.

=item Sequence (?%s...) not implemented

(F) A proposed regular expression extension has the character reserved
but has not yet been written.  See L<perlre>.

=item Sequence (?%s...) not recognized

(F) You used a regular expression extension that doesn't make sense.
See L<perlre>.

=item setegid() not implemented

(F) You tried to assign to $), and your operating system doesn't support
the setegid() system call (or equivalent), or at least Configure didn't
think so.

=item seteuid() not implemented

(F) You tried to assign to $>, and your operating system doesn't support
the seteuid() system call (or equivalent), or at least Configure didn't
think so.

=item setrgid() not implemented

(F) You tried to assign to $(, and your operating system doesn't support
the setrgid() system call (or equivalent), or at least Configure didn't
think so.

=item setruid() not implemented

(F) You tried to assign to $<, and your operating system doesn't support
the setruid() system call (or equivalent), or at least Configure didn't
think so.

=item Setuid/gid script is writable by world

(F) The setuid emulator won't run a script that is writable by the world,
because the world might have written on it already.

=item shm%s not implemented

(F) You don't have System V shared memory IPC on your system.

=item shutdown() on closed fd

(W) You tried to do a shutdown on a closed socket.  Seems a bit superfluous.

=item SIG%s handler "%s" not defined.

(W) The signal handler named in %SIG doesn't, in fact, exist.  Perhaps you
put it into the wrong package?

=item sort is now a reserved word

(F) An ancient error message that almost nobody ever runs into anymore.
But before sort was a keyword, people sometimes used it as a filehandle.

=item Sort subroutine didn't return a numeric value

(F) A sort comparison routine must return a number.  You probably blew
it by not using C<E<lt>=E<gt> or C<cmp>, or by not using them correctly.
See L<perlfunc/sort>.

=item Sort subroutine didn't return single value

(F) A sort comparison subroutine may not return a list value with more
or less than one element.  See L<perlfunc/sort>.

=item Split loop

(P) The split was looping infinitely.  (Obviously, a split shouldn't iterate
more times than there are characters of input, which is what happened.)
See L<perlfunc/split>.

=item Stat on unopened file <%s>

(W) You tried to use the stat() function (or an equivalent file test)
on a filehandle that was either never opened or has been closed since.

=item Statement unlikely to be reached

(W) You did an exec() with some statement after it other than a die().
This is almost always an error, because exec() never returns unless
there was a failure.  You probably wanted to use system() instead,
which does return.  To suppress this warning, put the exec() in a block
by itself.

=item Subroutine %s redefined

(W) You redefined a subroutine.  To suppress this warning, say

    {
	local $^W = 0;
	eval "sub name { ... }";
    }

=item Substitution loop

(P) The substitution was looping infinitely.  (Obviously, a
substitution shouldn't iterate more times than there are characters of
input, which is what happened.) See the discussion of substitution in
L<perlop/"Quote and Quotelike Operators">.

=item Substitution pattern not terminated

(F) The lexer couldn't find the interior delimiter of a s/// or s{}{}
construct.  Remember that bracketing delimiters count nesting level.

=item Substitution replacement not terminated

(F) The lexer couldn't find the final delimiter of a s/// or s{}{}
construct.  Remember that bracketing delimiters count nesting level.

=item substr outside of string

(W) You tried to reference a substr() that pointed outside of a string.
That is, the absolute value of the offset was larger than the length of
the string.  See L<perlfunc/substr>.

=item suidperl is no longer needed since...

(F) Your Perl was compiled with B<-D>SETUID_SCRIPTS_ARE_SECURE_NOW, but a
version of the setuid emulator somehow got run anyway.

=item syntax error

(F) Probably means you had a syntax error.  Common reasons include:

    A keyword is misspelled.
    A semicolon is missing.
    A comma is missing.
    An opening or closing parenthesis is missing.
    An opening or closing brace is missing.
    A closing quote is missing.

Often there will be another error message associated with the syntax
error giving more information.  (Sometimes it helps to turn on B<-w>.)
The error message itself often tells you where it was in the line when
it decided to give up.  Sometimes the actual error is several tokens
before this, since Perl is good at understanding random input.
Occasionally the line number may be misleading, and once in a blue moon
the only way to figure out what's triggering the error is to call
C<perl -c> repeatedly, chopping away half the program each time to see
if the error went away.  Sort of the cybernetic version of S<20 questions>.

=item System V IPC is not implemented on this machine

(F) You tried to do something with a function beginning with "sem", "shm"
or "msg".  See L<perlfunc/semctl>, for example.

=item Syswrite on closed filehandle

(W) The filehandle you're writing to got itself closed sometime before now.
Check your logic flow.

=item tell() on unopened file

(W) You tried to use the tell() function on a filehandle that was either
never opened or has been closed since.

=item Test on unopened file <%s>

(W) You tried to invoke a file test operator on a filehandle that isn't
open.  Check your logic.  See also L<perlfunc/-X>.

=item That use of $[ is unsupported

(F) Assignment to $[ is now strictly circumscribed, and interpreted as
a compiler directive.  You may only say one of

    $[ = 0;
    $[ = 1;
    ...
    local $[ = 0;
    local $[ = 1;
    ...

This is to prevent the problem of one module changing the array base
out from under another module inadvertently.  See L<perlvar/$[>.

=item The %s function is unimplemented

The function indicated isn't implemented on this architecture, according
to the probings of Configure.

=item The crypt() function is unimplemented due to excessive paranoia.

(F) Configure couldn't find the crypt() function on your machine,
probably because your vendor didn't supply it, probably because they
think the U.S. Govermnment thinks it's a secret, or at least that they
will continue to pretend that it is.  And if you quote me on that, I
will deny it.

=item The stat preceding C<-l _> wasn't an lstat

(F) It makes no sense to test the current stat buffer for symbolic linkhood
if the last stat that wrote to the stat buffer already went past
the symlink to get to the real file.  Use an actual filename instead.

=item times not implemented

(F) Your version of the C library apparently doesn't do times().  I suspect
you're not running on Unix.

=item Too few args to syscall

(F) There has to be at least one argument to syscall() to specify the
system call to call, silly dilly.

=item Too many args to syscall

(F) Perl only supports a maximum of 14 args to syscall().

=item Too many arguments for %s

(F) The function requires fewer arguments than you specified.

=item trailing \ in regexp

(F) The regular expression ends with an unbackslashed backslash.  Backslash
it.   See L<perlre>.

=item Translation pattern not terminated

(F) The lexer couldn't find the interior delimiter of a tr/// or tr[][]
construct.

=item Translation replacement not terminated

(F) The lexer couldn't find the final delimiter of a tr/// or tr[][]
construct.

=item truncate not implemented

(F) Your machine doesn't implement a file truncation mechanism that
Configure knows about.

=item Type of arg %d to %s must be %s (not %s)

(F) This function requires the argument in that position to be of a
certain type.  Arrays must be @NAME or @{EXPR}.  Hashes must be
%NAME or %{EXPR}.  No implicit dereferencing is allowed--use the
{EXPR} forms as an explicit dereference.  See L<perlref>.

=item umask: argument is missing initial 0

(W) A umask of 222 is incorrect.  It should be 0222, since octal literals
always start with 0 in Perl, as in C.

=item Unbalanced context: %d more PUSHes than POPs

(W) The exit code detected an internal inconsistency in how many execution
contexts were entered and left.

=item Unbalanced saves: %d more saves than restores

(W) The exit code detected an internal inconsistency in how many
values were temporarily localized.

=item Unbalanced scopes: %d more ENTERs than LEAVEs

(W) The exit code detected an internal inconsistency in how many blocks
were entered and left.

=item Unbalanced tmps: %d more allocs than frees

(W) The exit code detected an internal inconsistency in how many mortal
scalars were allocated and freed.

=item Undefined format "%s" called

(F) The format indicated doesn't seem to exist.  Perhaps it's really in
another package?  See L<perlform>.

=item Undefined sort subroutine "%s" called

(F) The sort comparison routine specified doesn't seem to exist.  Perhaps
it's in a different package?  See L<perlfunc/sort>.

=item Undefined subroutine &%s called

(F) The subroutine indicated hasn't been defined, or if it was, it
has since been undefined.

=item Undefined subroutine called

(F) The anonymous subroutine you're trying to call hasn't been defined,
or if it was, it has since been undefined.

=item Undefined subroutine in sort

(F) The sort comparison routine specified is declared but doesn't seem to
have been defined yet.  See L<perlfunc/sort>.

=item unexec of %s into %s failed!

(F) The unexec() routine failed for some reason.  See your local FSF
representative, who probably put it there in the first place.

=item Unknown BYTEORDER

(F) There are no byteswapping functions for a machine with this byte order.

=item unmatched () in regexp

(F) Unbackslashed parentheses must always be balanced in regular
expressions.  If you're a vi user, the % key is valuable for finding
the matching paren.  See L<perlre>.

=item Unmatched right bracket

(F) The lexer counted more closing curly brackets (braces) than opening
ones, so you're probably missing an opening bracket.  As a general
rule, you'll find the missing one (so to speak) near the place you were
last editing.

=item unmatched [] in regexp

(F) The brackets around a character class must match.  If you wish to
include a closing bracket in a character class, backslash it or put it first.
See L<perlre>.

=item Unquoted string "%s" may clash with future reserved word

(W) You used a bare word that might someday be claimed as a reserved word.
It's best to put such a word in quotes, or capitalize it somehow, or insert
an underbar into it.  You might also declare it as a subroutine.

=item Unrecognized character \%03o ignored

(S) A garbage character was found in the input, and ignored, in case it's
a weird control character on an EBCDIC machine, or some such.

=item Unrecognized signal name "%s"

(F) You specified a signal name to the kill() function that was not recognized.
Say C<kill -l> in your shell to see the valid signal names on your system.

=item Unrecognized switch: -%s

(F) You specified an illegal option to Perl.  Don't do that.
(If you think you didn't do that, check the #! line to see if it's
supplying the bad switch on your behalf.)

=item Unsuccessful %s on filename containing newline

(W) A file operation was attempted on a filename, and that operation
failed, PROBABLY because the filename contained a newline, PROBABLY
because you forgot to chop() or chomp() it off.  See L<perlfunc/chop>.

=item Unsupported directory function "%s" called

(F) Your machine doesn't support opendir() and readdir().

=item Unsupported function %s

(F) This machines doesn't implement the indicated function, apparently.
At least, Configure doesn't think so.

=item Unsupported socket function "%s" called

(F) Your machine doesn't support the Berkeley socket mechanism, or at
least that's what Configure thought.

=item Unterminated <> operator

(F) The lexer saw a left angle bracket in a place where it was expecting
a term, so it's looking for the corresponding right angle bracket, and not
finding it.  Chances are you left some needed parentheses out earlier in
the line, and you really meant a "less than".

=item Use of $# is deprecated

(D) This was an ill-advised attempt to emulate a poorly defined awk feature.
Use an explicit printf() or sprintf() instead.

=item Use of $* is deprecated

(D) This variable magically turned on multiline pattern matching, both for
you and for any luckless subroutine that you happen to call.  You should
use the new C<//m> and C<//s> modifiers now to do that without the dangerous
action-at-a-distance effects of C<$*>.

=item Use of %s is deprecated

(D) The construct indicated is no longer recommended for use, generally
because there's a better way to do it, and also because the old way has
bad side effects.

=item Use of implicit split to @_ is deprecated

(D) It makes a lot of work for the compiler when you clobber a
subroutine's argument list, so it's better if you assign the results of
a split() explicitly to an array (or list).

=item Use of uninitialized value

(W) An undefined value was used as if it were already defined.  It was
interpreted as a "" or a 0, but maybe it was a mistake.  To suppress this
warning assign an initial value to your variables.

=item Useless use of %s in void context

(W) You did something without a side effect in a context that does nothing
with the return value, such as a statement that doesn't return a value
from a block, or the left side of a scalar comma operator.  Very often
this points not to stupidity on your part, but a failure of Perl to parse
your program the way you thought it would.  For example, you'd get this
if you mixed up your C precedence with Python precedence and said

    $one, $two = 1, 2;

when you meant to say

    ($one, $two) = (1, 2);

=item Warning: unable to close filehandle %s properly.

(S) The implicit close() done by an open() got an error indication on the 
close(0.  This usually indicates your filesystem ran out of disk space.

=item Warning: Use of "%s" without parens is ambiguous

(S) You wrote a unary operator followed by something that looks like a
binary operator that could also have been interpreted as a term or
unary operator.  For instance, if you know that the rand function
has a default argument of 1.0, and you write

    rand + 5;

you may THINK you wrote the same thing as

    rand() + 5;

but in actual fact, you got

    rand(+5);

So put in parens to say what you really mean.

=item Write on closed filehandle

(W) The filehandle you're writing to got itself closed sometime before now.
Check your logic flow.

=item X outside of string

(F) You had a pack template that specified a relative position before
the beginning of the string being unpacked.  See L<perlfunc/pack>.

=item x outside of string

(F) You had a pack template that specified a relative position after
the end of the string being unpacked.  See L<perlfunc/pack>.

=item Xsub "%s" called in sort

(F) The use of an external subroutine as a sort comparison is not yet supported.

=item Xsub called in sort

(F) The use of an external subroutine as a sort comparison is not yet supported.

=item You can't use C<-l> on a filehandle

(F) A filehandle represents an opened file, and when you opened the file it
already went past any symlink you are presumably trying to look for.
Use a filename instead.

=item YOU HAVEN'T DISABLED SET-ID SCRIPTS IN THE KERNEL YET!

(F) And you probably never will, since you probably don't have the
sources to your kernel, and your vendor probably doesn't give a rip
about what you want.  Your best bet is to use the wrapsuid script in
the eg directory to put a setuid C wrapper around your script.

=item You need to quote "%s"

(W) You assigned a bareword as a signal handler name.  Unfortunately, you
already have a subroutine of that name declared, which means that Perl 5
will try to call the subroutine when the assignment is executed, which is
probably not what you want.  (If it IS what you want, put an & in front.)

=item [gs]etsockopt() on closed fd

(W) You tried to get or set a socket option on a closed socket.
Did you forget to check the return value of your socket() call?
See L<perlfunc/getsockopt>.

=item \1 better written as $1

(W) Outside of patterns, backreferences live on as variables.  The use
of backslashes is grandfathered on the righthand side of a
substitution, but stylistically it's better to use the variable form
because other Perl programmers will expect it, and it works better
if there are more than 9 backreferences.

=back