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use strict;
...
    keys %ipaddr;

print "$ipaddr{$_}\t$_\n" for @sortedKeys;

192.168.0.1     a
192.168.0.3     b
...
192.168.1.1     f
192.168.2.1     d
192.168.100.1   e

192.168.0.1     a
192.168.0.200   c
...
192.168.1.1     f
192.168.100.1   e
192.168.2.1     d