Odud's recent posting on Junior Perl came with a little
puzzle to do with giving change, which is simple enough,
and is certainly golf material.
Suppose you are trying to write a function c that,
give the amount you want, and an array reference to the
units of currency that you have available in order from
lowest to highest, will return a list of the required
change.

For instance, if $22.50 was specified, along with a US
currency specification, assuming no $2 bills are available
in the area:
print join(',',c(22.50,[.01,.05,.1,.25,1,5,10,20,50,100]));
Would output:
20,1,1,0.25,0.25
Of course, other countries use different units, such as:
print join(',',c(22.50,[.01,.05,.1,.20,1,2,5,10,20,50,100]));
Which would show:
20,2,0.2,0.2,0.1
Amounts less than the smallest unit of currency are not
handled, so they can be ignored.

Here's my baseline, which is 115 characters, not including
linebreaks required for presentation:

sub c{
($t,$p,@r)=@_;@p=map{int($_*100)}@$p;
$t=int($t*100);while($v=pop@p and$t>0
){while($t>=$v){push@r,$v/100;$t-=$v;
}}@r
}

You will note the use of integer math only. I am perplexed
by the floating point math. As Obdud says, this exercise
should teach "simple arithmetic, looping, lists, sorting,
etc." where 'etc.' apparently refers to floating point
idiosyncrasies, such as the following:
print "$t != $v\n" if ($t != $v);
Which surprisingly shows:
0.1 != 0.1
Where the values were actually: $t = 0.099999999999999977795540,
$v = 0.100000000000000005551115, due to some minor floating
point issues in the 17th decimal place.