.\" -*- mode: troff; coding: utf-8 -*- .\" Automatically generated by Pod::Man 5.01 (Pod::Simple 3.43) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" \*(C` and \*(C' are quotes in nroff, nothing in troff, for use with C<>. .ie n \{\ . ds C` "" . ds C' "" 'br\} .el\{\ . ds C` . ds C' 'br\} .\" .\" Escape single quotes in literal strings from groff's Unicode transform. .ie \n(.g .ds Aq \(aq .el .ds Aq ' .\" .\" If the F register is >0, we'll generate index entries on stderr for .\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index .\" entries marked with X<> in POD. Of course, you'll have to process the .\" output yourself in some meaningful fashion. .\" .\" Avoid warning from groff about undefined register 'F'. .de IX .. .nr rF 0 .if \n(.g .if rF .nr rF 1 .if (\n(rF:(\n(.g==0)) \{\ . if \nF \{\ . de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . if !\nF==2 \{\ . nr % 0 . nr F 2 . \} . \} .\} .rr rF .\" ======================================================================== .\" .IX Title "Symbol 3perl" .TH Symbol 3perl 2024-03-06 "perl v5.38.2" "Perl Programmers Reference Guide" .\" For nroff, turn off justification. Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH NAME Symbol \- manipulate Perl symbols and their names .SH SYNOPSIS .IX Header "SYNOPSIS" .Vb 1 \& use Symbol; \& \& $sym = gensym; \& open($sym, \*(Aq<\*(Aq, "filename"); \& $_ = <$sym>; \& # etc. \& \& ungensym $sym; # no effect \& \& # replace *FOO{IO} handle but not $FOO, %FOO, etc. \& *FOO = geniosym; \& \& print qualify("x"), "\en"; # "main::x" \& print qualify("x", "FOO"), "\en"; # "FOO::x" \& print qualify("BAR::x"), "\en"; # "BAR::x" \& print qualify("BAR::x", "FOO"), "\en"; # "BAR::x" \& print qualify("STDOUT", "FOO"), "\en"; # "main::STDOUT" (global) \& print qualify(\e*x), "\en"; # returns \e*x \& print qualify(\e*x, "FOO"), "\en"; # returns \e*x \& \& use strict refs; \& print { qualify_to_ref $fh } "foo!\en"; \& $ref = qualify_to_ref $name, $pkg; \& \& use Symbol qw(delete_package); \& delete_package(\*(AqFoo::Bar\*(Aq); \& print "deleted\en" unless exists $Foo::{\*(AqBar::\*(Aq}; .Ve .SH DESCRIPTION .IX Header "DESCRIPTION" \&\f(CW\*(C`Symbol::gensym\*(C'\fR creates an anonymous glob and returns a reference to it. Such a glob reference can be used as a file or directory handle. .PP For backward compatibility with older implementations that didn't support anonymous globs, \f(CW\*(C`Symbol::ungensym\*(C'\fR is also provided. But it doesn't do anything. .PP \&\f(CW\*(C`Symbol::geniosym\*(C'\fR creates an anonymous IO handle. This can be assigned into an existing glob without affecting the non-IO portions of the glob. .PP \&\f(CW\*(C`Symbol::qualify\*(C'\fR turns unqualified symbol names into qualified variable names (e.g. "myvar" \-> "MyPackage::myvar"). If it is given a second parameter, \f(CW\*(C`qualify\*(C'\fR uses it as the default package; otherwise, it uses the package of its caller. Regardless, global variable names (e.g. "STDOUT", "ENV", "SIG") are always qualified with "main::". .PP Qualification applies only to symbol names (strings). References are left unchanged under the assumption that they are glob references, which are qualified by their nature. .PP \&\f(CW\*(C`Symbol::qualify_to_ref\*(C'\fR is just like \f(CW\*(C`Symbol::qualify\*(C'\fR except that it returns a glob ref rather than a symbol name, so you can use the result even if \f(CW\*(C`use strict \*(Aqrefs\*(Aq\*(C'\fR is in effect. .PP \&\f(CW\*(C`Symbol::delete_package\*(C'\fR wipes out a whole package namespace. Note this routine is not exported by default\-\-you may want to import it explicitly. .SH BUGS .IX Header "BUGS" \&\f(CW\*(C`Symbol::delete_package\*(C'\fR is a bit too powerful. It undefines every symbol that lives in the specified package. Since perl, for performance reasons, does not perform a symbol table lookup each time a function is called or a global variable is accessed, some code that has already been loaded and that makes use of symbols in package \f(CW\*(C`Foo\*(C'\fR may stop working after you delete \f(CW\*(C`Foo\*(C'\fR, even if you reload the \f(CW\*(C`Foo\*(C'\fR module afterwards.