The English Module

The English module is designed to make your scripts more readable. It creates aliases for all of the special variables that were discussed in a previous chapter.

The following aliases that are defined in Table 15.1

   

$_ $ARG

@_ @ARG

$" $LIST_SEPARATOR

$; $SUBSCRIPT_SEPARATOR or $SUBSEP

$& $MATCH

$` $PREMATCH

$' $POSTMATCH

$+ $LAST_PAREN_MATCH

$. $INPUT_LINE_NUMBER or $NR

$/ $INPUT_RECORD_SEPARATOR or $RS

$| $OUTPUT_AUTOFLUSH

$, $OUTPUT_FIELD_SEPARATOR or $OFS

$\ $OUTPUT_RECORD_SEPARATOR or $ORS

$% $FORMAT_PAGE_NUMBER

$= $FORMAT_LINES_PER_PAGE

$_ $FORMAT_LINES_LEFT

$~ $FORMAT_NAME

$^ $FORMAT_TOP_NAME

$: $FORMAT_LINE_BREAK_CHARACTERS

$^L $FORMAT_FORMFEED

$? $CHILD_ERROR

$! $OS_ERROR or $ERRNO

$@ $EVAL_ERROR

$$ $PROCESS_ID or $PID

$< $REAL_USER_ID or $UID

$> $EFFECTIVE_USER_ID or $EUID

$( $REAL_GROUP_ID or $GID

$) $EFFECTIVE_GROUP_ID or $EGID

$0 $PROGRAM_NAME

$] $PERL_VERSION

$^A $AccUMULATOR

$^D $DEBUGGING

$^F $SYSTEM_FD_MAX

$^I $INPLACE_EDIT

$^P $PERLDB

$^T $BASETIME

$^W $WARNING

$^X $EXECUTABLE_NAME

Below is a program that uses one of the English variables to access information about a matched string. The program:

• Loads the English module.
• Invokes the strict pragma.
• Initializes the search space and pattern variables.
• Performs a matching operation to find the pattern in the $searchSpace variable.
• Displays information about the search.
• Displays the matching string using the English variable names.
• Displays the matching string using the standard Perl special variables.

The Perl code is as follows english.pl:

use English;

use strict;

my($searchSpace) = "TTTT BBBABBB DDDD";

my($pattern)     = "B+AB+";

$searchSpace =~ m/$pattern/;

print("Search space:   $searchSpace\n");

print("Pattern:        /$pattern/\n");

print("Matched String: $English::MATCH\n");  # the English variable

print("Matched String: $&\n");               # the standard Perl variable

This program displays:

Search space:   TTTT BBBABBB DDDD
Pattern:        /B+AB+/
Matched String: BBBABBB
Matched String: BBBABBB

You can see that the $& and $MATCH variables are equivalent. This means that you can use another programmer's functions without renaming their variables and still use the English names in your own functions.