use strict;
use warnings;
# A tiny private library routine which is a helper to several Perl core
# modules, to allow a paradigm to be implemented in a single place. The name,
# contents, or even the existence of this file may be changed at any time and
# are NOT to be used by anything outside the Perl core.
sub _meta_notation ($) {
# Returns a copy of the input string with the nonprintable characters
# below 0x100 changed into printables. Any ASCII printables or above 0xFF
# are unchanged. (XXX Probably above-Latin1 characters should be
# converted to \X{...})
#
# \0 .. \x1F (which are "\c@" .. "\c_") are changed into ^@, ^A, ^B, ...
# ^Z, ^[, ^\, ^], ^^, ^_
# \c? is changed into ^?.
#
# The above accounts for all the ASCII-range nonprintables.
#
# On ASCII platforms, the upper-Latin1-range characters are converted to
# Meta notation, so that \xC1 becomes 'M-A', \xE2 becomes 'M-b', etc.
# This is how it always has worked, so is continued that way for backwards
# compatibility. The range \x80 .. \x9F becomes M-^@ .. M-^A, M-^B, ...
# M-^Z, M-^[, M-^\, M-^], M-^, M-^_
#
# On EBCDIC platforms, the upper-Latin1-range characters are converted
# into '\x{...}' Meta notation doesn't make sense on EBCDIC platforms
# because the ASCII-range printables are a mixture of upper bit set or
# not. [A-Za-Z0-9] all have the upper bit set. The underscore likely
# doesn't; and other punctuation may or may not. There's no simple
# pattern.
my $string = shift;
$string =~ s/([\0-\037])/
sprintf("^%c",utf8::unicode_to_native(ord($1)^64))/xeg;
$string =~ s/\c?/^?/g;
if (ord("A") == 65) {
$string =~ s/([\200-\237])/sprintf("M-^%c",(ord($1)&0177)^64)/eg;
$string =~ s/([\240-\377])/sprintf("M-%c" ,ord($1)&0177)/eg;
}
else {
no warnings 'experimental::regex_sets';
# Leave alone things above \xff
$string =~ s/( (?[ [\x00-\xFF] & [:^print:]])) /
sprintf("\\x{%X}", ord($1))/xaeg;
}
return $string;
}
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