Perl: Functions by Category

Scalar manipulation
chomp, chop, chr, crypt, hex, index, lc, lcfirst, length, oct, ord, pack, q//, qq//, reverse, rindex, sprintf, substr, tr///, uc, ucfirst, y///

Regular expressions and pattern matching
m//, pos, qr//, quotemeta, s///, split, study

Numeric functions
abs, atan2, cos, exp, hex, int, log, oct, rand, sin, sqrt, srand

Array processing
pop, push, shift, splice, unshift

List processing
grep, join, map, qw//, reverse, sort, unpack

Hash processing
delete, each, exists, keys, values

Input and output
binmode, close, closedir, dbmclose, dbmopen, die, eof, fileno, flock, format, getc, print, printf, read, readdir, readpipe, rewinddir, seek, seekdir, select (ready file descriptors), syscall, sysread, sysseek, syswrite, tell, telldir, truncate, warn, write

Fixed-length data and records
pack, read, syscall, sysread, sysseek, syswrite, unpack, vec

Filehandles, files, and directories
chdir, chmod, chown, chroot, fcntl, glob, ioctl, link, lstat, mkdir, open, opendir, readlink, rename, rmdir, select (ready file descriptors), select (output filehandle), stat, symlink, sysopen, umask, unlink, utime

Flow of program control
caller, continue, die, do, dump, eval, exit, goto, last, next, redo, return, sub, wantarray

Scoping
caller, import, local, my, no, our, package, use

Miscellaneous
defined, dump, eval, formline, lock, prototype, reset, scalar, undef, wantarray

Processes and process groups
alarm, exec, fork, getpgrp, getppid, getpriority, kill, pipe, qx//, setpgrp, setpriority, sleep, system, times, wait, waitpid

Library modules
do, import, no, package, require, use

Classes and objects
bless, dbmclose, dbmopen, package, ref, tie, tied, untie, use

Low-level socket access
accept, bind, connect, getpeername, getsockname, getsockopt, listen, recv, send, setsockopt, shutdown, socket, socketpair

System V interprocess communication
msgctl, msgget, msgrcv, msgsnd, semctl, semget, semop, shmctl, shmget, shmread, shmwrite

Fetching user and group information
endgrent, endhostent, endnetent, endpwent, getgrent, getgrgid, getgrnam, getlogin, getpwent, getpwnam, getpwuid, setgrent, setpwent

Fetching network information
endprotoent, endservent, gethostbyaddr, gethostbyname, gethostent, getnetbyaddr, getnetbyname, getnetent, getprotobyname, getprotobynumber, getprotoent, getservbyname, getservbyport, getservent, sethostent, setnetent, setprotoent, setservent

Time
gmtime, localtime, time, times