use strict;
use Encode;
sub setConstants {
my $r = shift;
$r->{nichi} = decode(cp932 => '日');
$r->{getsu} = decode(cp932 => '月');
$r->{ka} = decode(cp932 => '火');
$r->{ka_length} = length($r->{ka});
$r->{sui} = decode(cp932 => '水');
$r->{moku} = decode(cp932 => '木');
$r->{kin} = decode(cp932 => '金');
$r->{do} = decode(cp932 => '土');
$r->{sun} = 'Sun';
$r->{mon} = 'Mon';
$r->{tue} = 'Tue';
$r->{wed} = 'Wed';
$r->{thu} = 'Thu';
$r->{fri} = 'Fri';
$r->{sat} = 'Sat';
}

# main
my ($i, $n, $s);
my $g = {};
my $line = decode(cp932 => '234 名前：デフォルトの名無しさん 投稿日：2012/07/17(火) 16:20:37.35 ');
setConstants($g);
$i = index($line, $g->{ka});
$n = $i + $g->{ka_length};
$s = join '', substr($line, 0, $i), $g->{tue}, substr($line, $n);
print encode(cp932 => $s), "\n";