my %code_map = ( euc => 'euc-jp',
                 sjis => 'shiftjis',
                 jis => 'iso-2022-jp',
                 ucs2 => 'UCS-2LE',  utf8 => 'utf8' );

# ...

my $kana_enc = getcode( $kana );

# ...

$kana_utf8 = decode( $code_map{$kana_enc}, $kana );

# ...