>>39
シフトJISだとこうかなあ。
$_ = 'ＴＢＣ個人情報３万件流出';
my @zenkaku = qw(
０ １ ２ ３ ４ ５ ６ ７ ８ ９
Ａ Ｂ Ｃ Ｄ Ｅ Ｆ Ｇ Ｈ Ｉ Ｊ Ｋ Ｌ Ｍ
Ｎ Ｏ Ｐ Ｑ Ｒ Ｓ Ｔ Ｕ Ｖ Ｗ Ｘ Ｙ Ｚ
ａ ｂ ｃ ｄ ｅ ｆ ｇ ｈ ｉ ｊ ｋ ｌ ｍ
ｎ ｏ ｐ ｑ ｒ ｓ ｔ ｕ ｖ ｗ ｘ ｙ ｚ);
my @hankaku = ("\x30".."\x39","\x41".."\x5A","\x61".."\x7A");
my %table;
@table{@zenkaku} = @hankaku;
s/(\x82[\x4F-\x9A])/$table{$1}/g;
print;

>>40
trは文字単位の置き換え。
$str1 = $str2 = 'abc abz';
$str1 =~ tr/abc/ABC/d;
$str2 =~ s/abc/ABC/g;
print "str1: ",$str1,"\n"; # ABC ABz
print "str2: ",$str2,"\n"; # ABC abz

>>43
帰れ。