$ perl -e '($n,$d)=split"/",pop;{1while++$x<$d/$n;warn"1/$x\n";$n=$n*$x-$d;$d*=$x;redo if$n}' 18/20
1/2
1/3
1/15

##</code><code>##

for(($n,$d)=split"/",pop;$n;){1while++$x<$d/$n;warn"1/$x\n";$n=$n*$x-$d;$d*=$x}

##</code><code>##

perl -e '$f=eval pop;{1while++$x<1/$f;warn"1/$x\n";redo if$f-=1/$x}' 19/20