DB<15> %h2 = pairgrep { $b =~ /[aeiou]/ } %h

  DB<16> x \%h2
0  HASH(0x349ee60)
   1 => 'a'
   15 => 'o'
   21 => 'u'
   5 => 'e'
   9 => 'i'
  DB<17>