Followed example online, I am trying to filter IP address from a networkctl report. 
#!/usr/bin/perl
use strict;
use warnings;
use Regexp::Common qw(net);
use String::Util qw(trim);

while (<>) {
    /$RE{net}{IPv4}{-keep}/                                and printf 
+"%s\n", trim($1);
    /$RE{net}{IPv6}{-sep => ':'}{-style => 'HeX'}{-keep}/  and printf 
+"%s\n", trim($1);
    /$RE{net}{MAC}{-keep}/                                 and printf 
+"%s\n", trim($1);
}

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by running 
 
cat report.txt | ./ips.pl > ips.txt

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Then I used vi's dd to remove lines and got this file (remove real IPs and MAC address before posting here) 
192.168.1.188
fdba:7b43:1916::d34
fe80::ec78:4ff:fec0:a17b
192.168.1.1
fe80::eade:27ff:feb6:fa8c
192.168.1.1
fdba:7b43:1916::1
fdba:7b43:1916::d34
fdba:7b43:1916::d34
fdba:7b43:1916::d34
fdba:7b43:1916::d34
fdba:7b43:1916::d34

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When I further filter with GNU coreutil's uniq, I got different results from "uniq" Vs "uniq -u". I read online that this is mainly due to spaces in the data file. When I print in the perl script, I trim() already. What might went wrong in the above script? 
cat perlout.txt | sort | uniq
192.168.1.1
192.168.1.188
fdba:7b43:1916::1
fdba:7b43:1916::d34
fe80::eade:27ff:feb6:fa8c
fe80::ec78:4ff:fec0:a17b

cat perlout.txt | sort | uniq -u
192.168.1.188
fdba:7b43:1916::1
fe80::eade:27ff:feb6:fa8c
fe80::ec78:4ff:fec0:a17b

When pre-filter one more time with uniq, then they give same result
cat perlout.txt | sort | uniq | uniq
192.168.1.1
192.168.1.188
fdba:7b43:1916::1
fdba:7b43:1916::d34
fe80::eade:27ff:feb6:fa8c
fe80::ec78:4ff:fec0:a17b

cat perlout.txt  | sort | uniq | uniq -u
192.168.1.1
192.168.1.188
fdba:7b43:1916::1
fdba:7b43:1916::d34
fe80::eade:27ff:feb6:fa8c
fe80::ec78:4ff:fec0:a17b

[download]

In reply to Perl output and uniq by sampson

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