📄 perlfaq.pod
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=head1 NAMEperlfaq - frequently asked questions about Perl ($Date: 1999/05/23 20:38:02 $)=head1 DESCRIPTIONThe perlfaq is structured into the following documents:=head2 perlfaq: Structural overview of the FAQ.This document.=head2 L<perlfaq1>: General Questions About PerlVery general, high-level information about Perl.=over 4=item *What is Perl?=item *Who supports Perl? Who develops it? Why is it free?=item *Which version of Perl should I use?=item *What are perl4 and perl5?=item *What is perl6?=item *How stable is Perl?=item *Is Perl difficult to learn?=item *How does Perl compare with other languages like Java, Python, REXX, Scheme, or Tcl?=item *Can I do [task] in Perl?=item *When shouldn't I program in Perl?=item *What's the difference between "perl" and "Perl"?=item *Is it a Perl program or a Perl script?=item *What is a JAPH?=item *Where can I get a list of Larry Wall witticisms?=item *How can I convince my sysadmin/supervisor/employees to use version 5/5.005/Perl instead of some other language?=back=head2 L<perlfaq2>: Obtaining and Learning about PerlWhere to find source and documentation to Perl, support,and related matters.=over 4=item *What machines support Perl? Where do I get it?=item *How can I get a binary version of Perl?=item *I don't have a C compiler on my system. How can I compile perl?=item *I copied the Perl binary from one machine to another, but scripts don't work.=item *I grabbed the sources and tried to compile but gdbm/dynamic loading/malloc/linking/... failed. How do I make it work?=item *What modules and extensions are available for Perl? What is CPAN? What does CPAN/src/... mean?=item *Is there an ISO or ANSI certified version of Perl?=item *Where can I get information on Perl?=item *What are the Perl newsgroups on Usenet? Where do I post questions?=item *Where should I post source code?=item *Perl Books=item *Perl in Magazines=item *Perl on the Net: FTP and WWW Access=item *What mailing lists are there for Perl?=item *Archives of comp.lang.perl.misc=item *Where can I buy a commercial version of Perl?=item *Where do I send bug reports?=item *What is perl.com? Perl Mongers? pm.org? perl.org?=back=head2 L<perlfaq3>: Programming ToolsProgrammer tools and programming support.=over 4=item *How do I do (anything)?=item *How can I use Perl interactively?=item *Is there a Perl shell?=item *How do I debug my Perl programs?=item *How do I profile my Perl programs?=item *How do I cross-reference my Perl programs?=item *Is there a pretty-printer (formatter) for Perl?=item *Is there a ctags for Perl?=item *Is there an IDE or Windows Perl Editor?=item *Where can I get Perl macros for vi?=item *Where can I get perl-mode for emacs?=item *How can I use curses with Perl?=item *How can I use X or Tk with Perl?=item *How can I generate simple menus without using CGI or Tk?=item *What is undump?=item *How can I make my Perl program run faster?=item *How can I make my Perl program take less memory?=item *Is it unsafe to return a pointer to local data?=item *How can I free an array or hash so my program shrinks?=item *How can I make my CGI script more efficient?=item *How can I hide the source for my Perl program?=item *How can I compile my Perl program into byte code or C?=item *How can I compile Perl into Java?=item *How can I get C<#!perl> to work on [MS-DOS,NT,...]?=item *Can I write useful Perl programs on the command line?=item *Why don't Perl one-liners work on my DOS/Mac/VMS system?=item *Where can I learn about CGI or Web programming in Perl?=item *Where can I learn about object-oriented Perl programming?=item *Where can I learn about linking C with Perl? [h2xs, xsubpp]=item *I've read perlembed, perlguts, etc., but I can't embed perl inmy C program; what am I doing wrong?=item *When I tried to run my script, I got this message. What does itmean?=item *What's MakeMaker?=back=head2 L<perlfaq4>: Data ManipulationManipulating numbers, dates, strings, arrays, hashes, andmiscellaneous data issues.=over 4=item *Why am I getting long decimals (eg, 19.9499999999999) instead of the numbers I should be getting (eg, 19.95)?=item *Why isn't my octal data interpreted correctly?=item *Does Perl have a round() function? What about ceil() and floor()? Trig functions?=item *How do I convert bits into ints?=item *Why doesn't & work the way I want it to?=item *How do I multiply matrices?=item *How do I perform an operation on a series of integers?=item *How can I output Roman numerals?=item *Why aren't my random numbers random?=item *How do I find the week-of-the-year/day-of-the-year?=item *How do I find the current century or millennium?=item *How can I compare two dates and find the difference?=item *How can I take a string and turn it into epoch seconds?=item *How can I find the Julian Day?=item *How do I find yesterday's date?=item *Does Perl have a Year 2000 problem? Is Perl Y2K compliant?=item *How do I validate input?=item *How do I unescape a string?=item *How do I remove consecutive pairs of characters?=item *How do I expand function calls in a string?=item *How do I find matching/nesting anything?=item *How do I reverse a string?=item *How do I expand tabs in a string?=item *How do I reformat a paragraph?=item *How can I access/change the first N letters of a string?=item *How do I change the Nth occurrence of something?=item *How can I count the number of occurrences of a substring within a string?=item *How do I capitalize all the words on one line?=item *How can I split a [character] delimited string except when inside[character]? (Comma-separated files)=item *How do I strip blank space from the beginning/end of a string?=item *How do I pad a string with blanks or pad a number with zeroes?=item *How do I extract selected columns from a string?=item *How do I find the soundex value of a string?=item *How can I expand variables in text strings?=item *What's wrong with always quoting "$vars"?=item *Why don't my <<HERE documents work?=item *What is the difference between a list and an array?=item *What is the difference between $array[1] and @array[1]?=item *How can I remove duplicate elements from a list or array?=item *How can I tell whether a list or array contains a certain element?=item *How do I compute the difference of two arrays? How do I compute the intersection of two arrays?=item *How do I test whether two arrays or hashes are equal?=item *How do I find the first array element for which a condition is true?=item *How do I handle linked lists?=item *How do I handle circular lists?=item *How do I shuffle an array randomly?=item *How do I process/modify each element of an array?=item *How do I select a random element from an array?=item *How do I permute N elements of a list?=item *How do I sort an array by (anything)?=item *How do I manipulate arrays of bits?=item *Why does defined() return true on empty arrays and hashes?=item *How do I process an entire hash?=item *What happens if I add or remove keys from a hash while iterating over it?=item *How do I look up a hash element by value?=item *How can I know how many entries are in a hash?=item *How do I sort a hash (optionally by value instead of key)?=item *How can I always keep my hash sorted?=item *What's the difference between "delete" and "undef" with hashes?=item *Why don't my tied hashes make the defined/exists distinction?=item *How do I reset an each() operation part-way through?=item *How can I get the unique keys from two hashes?=item *How can I store a multidimensional array in a DBM file?=item *How can I make my hash remember the order I put elements into it?=item *Why does passing a subroutine an undefined element in a hash create it?=item *How can I make the Perl equivalent of a C structure/C++ class/hash or array of hashes or arrays?=item *How can I use a reference as a hash key?=item *How do I handle binary data correctly?=item *How do I determine whether a scalar is a number/whole/integer/float?=item *How do I keep persistent data across program calls?=item *How do I print out or copy a recursive data structure?=item *How do I define methods for every class/object?=item *How do I verify a credit card checksum?=item *How do I pack arrays of doubles or floats for XS code?=back=head2 L<perlfaq5>: Files and FormatsI/O and the "f" issues: filehandles, flushing, formats and footers.=over 4=item *How do I flush/unbuffer an output filehandle? Why must I do this?=item *How do I change one line in a file/delete a line in a file/insert a line in the middle of a file/append to the beginning of a file?=item *How do I count the number of lines in a file?=item *How do I make a temporary file name?=item *How can I manipulate fixed-record-length files?=item *How can I make a filehandle local to a subroutine? How do I pass filehandles between subroutines? How do I make an array of filehandles?=item *How can I use a filehandle indirectly?=item *How can I set up a footer format to be used with write()?=item *How can I write() into a string?=item *How can I output my numbers with commas added?=item *How can I translate tildes (~) in a filename?=item *How come when I open a file read-write it wipes it out?=item *Why do I sometimes get an "Argument list too long" when I use <*>?=item *Is there a leak/bug in glob()?=item *How can I open a file with a leading ">" or trailing blanks?=item *How can I reliably rename a file?=item *How can I lock a file?=item *Why can't I just open(FH, ">file.lock")?=item *I still don't get locking. I just want to increment the number in the file. How can I do this?=item *How do I randomly update a binary file?=item *How do I get a file's timestamp in perl?=item *How do I set a file's timestamp in perl?=item *How do I print to more than one file at once?=item *How can I read in an entire file all at once?=item *How can I read in a file by paragraphs?⌨️ 快捷键说明
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