sub hole_one{(pop=~/\w+/g)[4]}
#16 characters
hole two:
perl -e "print STDERR 'Can\'t find label TPC at -e line 5.'"
#60 characters (using tachyon's method)
sub hole_three{pop=~/^(.*?)\1+$/s}
#18 characters (handles carriage returns in the input)
sub hole_four{map{chr hex}(pop=~/(..)/g)}
#26 characters
sub hole_five{$a=pop;(grep{$a=$_ if $_>$a}@_)[-1]}
#35 characters (updated for negetive numbers)
sub hole_six{sort{($a=~/([aeiou])/)[0]cmp($b=~//)[0]}@_}
#42 characters