in reply to Binary Coded Decimal

sub bcd
{
    local $_ = shift;
    
    # enforce two digits
    $_ = "0$_" while 2 > length;
    die "too big" unless m{^(\d)(\d)$};
    
    return chr(16*$1 + $2);
}

[download]
perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

In Section Seekers of Perl Wisdom