charnames - define character names for \N{named} string literal escape.
use charnames ':full';
print "\N{GREEK SMALL LETTER SIGMA} is called sigma.\n";
use charnames ':short';
print "\N{greek:Sigma} is an upper-case sigma.\n";
use charnames qw(cyrillic greek);
print "\N{sigma} is Greek sigma, and \N{be} is Cyrillic b.\n";
Pragma use charnames supports arguments :full, :short and
script names. If :full is present, for expansion of
\N{CHARNAME}} string CHARNAME is first looked in the list of
standard Unicode names of chars. If :short is present, and
CHARNAME has the form SCRIPT:CNAME, then CNAME is looked up
as a letter in script SCRIPT. If pragma use charnames is used
with script name arguments, then for \N{CHARNAME}} the name
CHARNAME is looked up as a letter in the given scripts (in the
specified order).
For lookup of CHARNAME inside a given script SCRIPTNAME
this pragma looks for the names
SCRIPTNAME CAPITAL LETTER CHARNAME
SCRIPTNAME SMALL LETTER CHARNAME
SCRIPTNAME LETTER CHARNAME
in the table of standard Unicode names. If CHARNAME is lowercase,
then the CAPITAL variant is ignored, otherwise the SMALL variant is
ignored.
The mechanism of translation of \N{...} escapes is general and not
hardwired into charnames.pm. A module can install custom
translations (inside the scope which uses the module) with the
following magic incantation:
use charnames (); # for $charnames::hint_bits
sub import {
shift;
$^H |= $charnames::hint_bits;
$^H{charnames} = \&translator;
}
Here translator() is a subroutine which takes CHARNAME as an
argument, and returns text to insert into the string instead of the
\N{CHARNAME} escape. Since the text to insert should be different
in bytes mode and out of it, the function should check the current
state of bytes-flag as in:
use bytes (); # for $bytes::hint_bits
sub translator {
if ($^H & $bytes::hint_bits) {
return bytes_translator(@_);
}
else {
return utf8_translator(@_);
}
}
Since evaluation of the translation function happens in a middle of
compilation (of a string literal), the translation function should not
do any evals or requires. This restriction should be lifted in
a future version of Perl.
