English.pm: Update -no_match_vars docs

[perl5.git] / lib / English.pm

package English;

our $VERSION = '1.05';

require Exporter;
@ISA = qw(Exporter);

=head1 NAME

English - use nice English (or awk) names for ugly punctuation variables

=head1 SYNOPSIS

    use English;
    use English qw( -no_match_vars ) ;  # Avoids regex performance penalty
                                        # in perl 5.16 and earlier
    ...
    if ($ERRNO =~ /denied/) { ... }

=head1 DESCRIPTION

This module provides aliases for the built-in variables whose
names no one seems to like to read.  Variables with side-effects
which get triggered just by accessing them (like $0) will still 
be affected.

For those variables that have an B<awk> version, both long
and short English alternatives are provided.  For example, 
the C<$/> variable can be referred to either $RS or 
$INPUT_RECORD_SEPARATOR if you are using the English module.

See L<perlvar> for a complete list of these.

=head1 PERFORMANCE

NOTE: This was fixed in perl 5.18.  Mentioning these three variables no
longer makes a speed difference.  This section still applies if your code
is to run on perl 5.16 or earlier.

This module can provoke sizeable inefficiencies for regular expressions,
due to unfortunate implementation details.  If performance matters in
your application and you don't need $PREMATCH, $MATCH, or $POSTMATCH,
try doing

   use English qw( -no_match_vars ) ;

.  B<It is especially important to do this in modules to avoid penalizing
all applications which use them.>

=cut

no warnings;

my $globbed_match ;

# Grandfather $NAME import
sub import {
    my $this = shift;
    my @list = grep { ! /^-no_match_vars$/ } @_ ;
    local $Exporter::ExportLevel = 1;
    if ( @_ == @list ) {
        *EXPORT = \@COMPLETE_EXPORT ;
        $globbed_match ||= (
	    eval q{
		*MATCH				= *&	;
		*PREMATCH			= *`	;
		*POSTMATCH			= *'	;
		1 ;
	       }
	    || do {
		require Carp ;
		Carp::croak("Can't create English for match leftovers: $@") ;
	    }
	) ;
    }
    else {
        *EXPORT = \@MINIMAL_EXPORT ;
    }
    Exporter::import($this,grep {s/^\$/*/} @list);
}

@MINIMAL_EXPORT = qw(
	*ARG
	*LAST_PAREN_MATCH
	*INPUT_LINE_NUMBER
	*NR
	*INPUT_RECORD_SEPARATOR
	*RS
	*OUTPUT_AUTOFLUSH
	*OUTPUT_FIELD_SEPARATOR
	*OFS
	*OUTPUT_RECORD_SEPARATOR
	*ORS
	*LIST_SEPARATOR
	*SUBSCRIPT_SEPARATOR
	*SUBSEP
	*FORMAT_PAGE_NUMBER
	*FORMAT_LINES_PER_PAGE
	*FORMAT_LINES_LEFT
	*FORMAT_NAME
	*FORMAT_TOP_NAME
	*FORMAT_LINE_BREAK_CHARACTERS
	*FORMAT_FORMFEED
	*CHILD_ERROR
	*OS_ERROR
	*ERRNO
	*EXTENDED_OS_ERROR
	*EVAL_ERROR
	*PROCESS_ID
	*PID
	*REAL_USER_ID
	*UID
	*EFFECTIVE_USER_ID
	*EUID
	*REAL_GROUP_ID
	*GID
	*EFFECTIVE_GROUP_ID
	*EGID
	*PROGRAM_NAME
	*PERL_VERSION
	*ACCUMULATOR
	*COMPILING
	*DEBUGGING
	*SYSTEM_FD_MAX
	*INPLACE_EDIT
	*PERLDB
	*BASETIME
	*WARNING
	*EXECUTABLE_NAME
	*OSNAME
	*LAST_REGEXP_CODE_RESULT
	*EXCEPTIONS_BEING_CAUGHT
	*LAST_SUBMATCH_RESULT
	@LAST_MATCH_START
	@LAST_MATCH_END
);


@MATCH_EXPORT = qw(
	*MATCH
	*PREMATCH
	*POSTMATCH
);

@COMPLETE_EXPORT = ( @MINIMAL_EXPORT, @MATCH_EXPORT ) ;

# The ground of all being.

	*ARG					= *_	;

# Matching.

	*LAST_PAREN_MATCH			= *+	;
	*LAST_SUBMATCH_RESULT			= *^N ;
	*LAST_MATCH_START			= *-{ARRAY} ;
	*LAST_MATCH_END				= *+{ARRAY} ;

# Input.

	*INPUT_LINE_NUMBER			= *.	;
	    *NR					= *.	;
	*INPUT_RECORD_SEPARATOR			= */	;
	    *RS					= */	;

# Output.

	*OUTPUT_AUTOFLUSH			= *|	;
	*OUTPUT_FIELD_SEPARATOR			= *,	;
	    *OFS				= *,	;
	*OUTPUT_RECORD_SEPARATOR		= *\	;
	    *ORS				= *\	;

# Interpolation "constants".

	*LIST_SEPARATOR				= *"	;
	*SUBSCRIPT_SEPARATOR			= *;	;
	    *SUBSEP				= *;	;

# Formats

	*FORMAT_PAGE_NUMBER			= *%	;
	*FORMAT_LINES_PER_PAGE			= *=	;
	*FORMAT_LINES_LEFT			= *-	;
	*FORMAT_NAME				= *~	;
	*FORMAT_TOP_NAME			= *^	;
	*FORMAT_LINE_BREAK_CHARACTERS		= *:	;
	*FORMAT_FORMFEED			= *^L	;

# Error status.

	*CHILD_ERROR				= *?	;
	*OS_ERROR				= *!	;
	    *ERRNO				= *!	;
	*OS_ERROR				= *!	;
	    *ERRNO				= *!	;
	*EXTENDED_OS_ERROR			= *^E	;
	*EVAL_ERROR				= *@	;

# Process info.

	*PROCESS_ID				= *$	;
	    *PID				= *$	;
	*REAL_USER_ID				= *<	;
	    *UID				= *<	;
	*EFFECTIVE_USER_ID			= *>	;
	    *EUID				= *>	;
	*REAL_GROUP_ID				= *(	;
	    *GID				= *(	;
	*EFFECTIVE_GROUP_ID			= *)	;
	    *EGID				= *)	;
	*PROGRAM_NAME				= *0	;

# Internals.

	*PERL_VERSION				= *^V	;
	*ACCUMULATOR				= *^A	;
	*COMPILING				= *^C	;
	*DEBUGGING				= *^D	;
	*SYSTEM_FD_MAX				= *^F	;
	*INPLACE_EDIT				= *^I	;
	*PERLDB					= *^P	;
	*LAST_REGEXP_CODE_RESULT		= *^R	;
	*EXCEPTIONS_BEING_CAUGHT		= *^S	;
	*BASETIME				= *^T	;
	*WARNING				= *^W	;
	*EXECUTABLE_NAME			= *^X	;
	*OSNAME					= *^O	;

# Deprecated.

#	*ARRAY_BASE				= *[	;
#	*OFMT					= *#	;
#	*OLD_PERL_VERSION			= *]	;

1;