What are Perl built-in operators/functions?

The built-in operators are not Perl subroutines. For example, 

#!/usr/bin/perl

use strict;
use warnings;

sub Foo { print "In foo\n"; }

my $ref;

$ref = \&Foo;
$ref->();

$ref = \&print;
$ref->();

The first $ref->(); is an indirect call; it prints "In foo".

The second one produces a warning:

Undefined subroutine &main::print called at ./tmp.pl line 14

because print is not the name of a subroutine.


The Perl keywords are those defined in the regen/keywords.pl file within the Perl source distribution. These are:

__FILE__, __LINE__, __PACKAGE__, __DATA__, __END__, AUTOLOAD, BEGIN, UNITCHECK, CORE, DESTROY, END, INIT, CHECK, abs, accept, alarm, and, atan2, bind, binmode, bless, break, caller, chdir, chmod, chomp, chop, chown, chr, chroot, close, closedir, cmp, connect, continue, cos, crypt, dbmclose, dbmopen, default, defined, delete, die, do, dump, each, else, elsif, endgrent, endhostent, endnetent, endprotoent, endpwent, endservent, eof, eq, eval, exec, exists, exit, exp, fcntl, fileno, flock, for, foreach, fork, format, formline, ge, getc, getgrent, getgrgid, getgrnam, gethostbyaddr, gethostbyname, gethostent, getlogin, getnetbyaddr, getnetbyname, getnetent, getpeername, getpgrp, getppid, getpriority, getprotobyname, getprotobynumber, getprotoent, getpwent, getpwnam, getpwuid, getservbyname, getservbyport, getservent, getsockname, getsockopt, given, glob, gmtime, goto, grep, gt, hex, if, index, int, ioctl, join, keys, kill, last, lc, lcfirst, le, length, link, listen, local, localtime, lock, log, lstat, lt, m, map, mkdir, msgctl, msgget, msgrcv, msgsnd, my, ne, next, no, not, oct, open, opendir, or, ord, our, pack, package, pipe, pop, pos, print, printf, prototype, push, q, qq, qr, quotemeta, qw, qx, rand, read, readdir, readline, readlink, readpipe, recv, redo, ref, rename, require, reset, return, reverse, rewinddir, rindex, rmdir, s, say, scalar, seek, seekdir, select, semctl, semget, semop, send, setgrent, sethostent, setnetent, setpgrp, setpriority, setprotoent, setpwent, setservent, setsockopt, shift, shmctl, shmget, shmread, shmwrite, shutdown, sin, sleep, socket, socketpair, sort, splice, split, sprintf, sqrt, srand, stat, state, study, sub, substr, symlink, syscall, sysopen, sysread, sysseek, system, syswrite, tell, telldir, tie, tied, time, times, tr, truncate, uc, ucfirst, umask, undef, unless, unlink, unpack, unshift, untie, until, use, utime, values, vec, wait, waitpid, wantarray, warn, when, while, write, x, xor, y.

The perlsyn, perlop, and perlsub manpages are required reading, followed perhaps by the perlfunc manpage. To learn how to override builtin operators used with objects, see the overload manpage.


print, open, split are not subroutines. They do not result in sub calls. They are not even present in the symbol table (in main:: or otherwise, although you can refer to them as CORE::split, etc), and one cannot get a reference to their code (although work is being done to create proxy subs for them in CORE:: for when you want to treat them as subroutines). They are operators just like +.

$ perl -MO=Concise,-exec -e'sub f {} f()'
1  <0> enter 
2  <;> nextstate(main 2 -e:1) v:{
3  <0> pushmark s
4  <#> gv[*f] s
5  <1> entersub[t3] vKS/TARG,1      <--- sub call
6  <@> leave[1 ref] vKP/REFC
-e syntax OK

$ perl -MO=Concise,-exec -e'split /;/'
1  <0> enter 
2  <;> nextstate(main 1 -e:1) v:{
3  </> pushre(/";"/) s/64
4  <#> gvsv[*_] s
5  <$> const[IV 0] s
6  <@> split[t2] vK                 <--- not a sub call
7  <@> leave[1 ref] vKP/REFC
-e syntax OK

$ perl -MO=Concise,-exec -e'$x + $y'
1  <0> enter 
2  <;> nextstate(main 1 -e:1) v:{
3  <#> gvsv[*x] s
4  <#> gvsv[*y] s
5  <2> add[t3] vK/2                 <--- Just like this
6  <@> leave[1 ref] vKP/REFC
-e syntax OK

They are known by a variety of names:

  • builtin functions
  • functions
  • builtins
  • named operators

And most are considered to be one of the following:

  • list operator
  • named unary operator

Subroutines are often called functions (as they are in C and C++), so "function" is an ambiguous word. This ambiguity appears to be the basis of your question.

As for while, for, unless, etc, they are keywords used by flow control statements

while (f()) { g() }

and statement modifiers

g() while f();

Tags:

Perl

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