gistfile1.perl

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

sub modhash(&\%) {
    my ($sub,$h) = @_;
    foreach my $k (keys %$h) {
        my $v = delete $h->{$k};
        ($k,$v) = $sub->($k,$v);
        $h->{$k} = $v;
    }
}

my %h = (foo => 'oof', bar => 'rab');

modhash { (uc($_[0]), uc(reverse($_[1]))) } %h;

print Dumper(\%h);