It's there because in your OP you say "... I need to identify on what host each user-id ...". It's not used because I didn't need it to illustrate the main issue. However if you change the final print to:

for my $name (@unlike) {
    my @hosts = map {$entries{$name}{$_}{host}} keys %{$entries{$name}
+};
    print "$name found on \n\t", join ("\n\t", @hosts), "\n\n";
}

[download]

then the output is:

bjose found on 
    /var/tmp/passwd.hostname2.platform
    /var/tmp/passwd.hostname1.platform

[download]
DWIM is Perl's answer to Gödel

In reply to Re^3: trying to decide best data structure for problem at hand. by GrandFather
in thread trying to decide best data structure for problem at hand. by mikejones

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