#!perl -w
use strict;
use Data::Dumper 'Dumper';

my %ranges = (
  a => [11,22],
  b => [22,45], # etc
);

my %r2 = %ranges; # need copy to reentrantly iterate over %ranges
                  # perl sucks sometimes.
my %results;
while (my ($name,$range) = each %ranges) {
   while (my ($name2,$range2) = each %r2) {
     if ($name ne $name2 and $range->[0] <= $range2->[0] && $range->[1] >= $range2->[0]) {
       push @{$results{$name}},$name2;
     }
   }
   $results{$name} ||= [];
}

print Dumper(\%results);