TIMTOWTDI!

But instead of reinventing the wheel, there is a pairgrep and pairmap in (newer°) List::Util, which is core

debugger-demo (via perl -de0 ) 

  DB<10> @h{1..26} = a..z

  DB<11> use List::Util qw/pairgrep/

  DB<12> x pairgrep { $b =~ /[aeiou]/ } %h
0  15
1  'o'
2  21
3  'u'
4  9
5  'i'
6  5
7  'e'
8  1
9  'a'
  DB<13> use List::Util qw/pairmap/

  DB<14> x pairmap { $b =~ /[aeiou]/ ? [$a => $b] : () } %h
0  ARRAY(0x349eed8)
   0  15
   1  'o'
1  ARRAY(0x349ef20)
   0  21
   1  'u'
2  ARRAY(0x349ef80)
   0  9
   1  'i'
3  ARRAY(0x349efe0)
   0  5
   1  'e'
4  ARRAY(0x349f040)
   0  1
   1  'a'
  DB<15>

[download]

update

Perl doesn't have datatype for pairs, but you could use a second hash for shorter syntax :) 

  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>

[download]

update

°) came into core with 5.20.0 i.e. since May 27, 2014. So only new for oldies like me ;-)

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery

In reply to Re: How to grep for values & see the keys? by LanX
in thread How to grep for values & see the keys? by misterperl

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