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copied!<p>If I understand your issue correctly, you want to add items from the template hash to the user settings' hash <em>only if</em> those items from the template hash do not exist within the users' settings hash.</p> <p>We can take advantage of Perl's <a href="http://en.wikipedia.org/wiki/Autovivification" rel="nofollow">Autovivification</a> which will create the complete data structure within the user settings' hash if an item in that hash doesn't exist. Consider the following:</p> <pre><code>use strict; use warnings; use Data::Dumper; my %template = ( 'Hotkeys' => [ 'key', 'keyCR', 'keyHighlight', 'updated' ], 'Actions' => [ 'action', 'actionCR', 'actionHighlight' ], 'Settings' => [ 'chbAcronym', 'chbCompleted' ], 'NewSetting' => [ 'NewValue' ] ); my %userSettings = ( 'Hotkeys' => [ 'key', 'keyCR', 'keyHighlight' ], 'Actions' => [ 'action', 'actionCR', 'actionHighlight' ], 'Settings' => [ 'chbAcronym', 'chbCompleted', 'aUserSetting' ] ); updateUserSettings( \%template, \%userSettings ); print Dumper \%userSettings; sub updateUserSettings { my ( $templateHash, $settingsHash ) = @_; for my $key ( keys %$templateHash ) { $settingsHash->{$key}->[$_] //= $templateHash->{$key}->[$_] for 0 .. $#{ ${$templateHash}{$key} }; } } </code></pre> <p>Output (a dump of <code>%userSettings</code> after the 'update'):</p> <pre><code>$VAR1 = { 'Hotkeys' => [ 'key', 'keyCR', 'keyHighlight', 'updated' ], 'Actions' => [ 'action', 'actionCR', 'actionHighlight' ], 'NewSetting' => [ 'NewValue' ], 'Settings' => [ 'chbAcronym', 'chbCompleted', 'aUserSetting' ] } </code></pre> <p>Note that <code>%userSettings</code> is only updated with missing <code>%template</code> information and nothing else is disturbed.</p> <p>The subroutine <code>updateUserSettings</code> uses Perl's <em>defined-or</em> (<code>//=</code>) operator as it iterates through all the keys of <code>%template</code>, so <code>%userSettings</code> isn't changed if a key/value already exists, otherwise it updated.</p> <p>Hope this helps!</p>

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