diff --git a/lib/calcms/audio_recordings.pm b/lib/calcms/audio_recordings.pm
index 0eb4666..a7b0195 100644
--- a/lib/calcms/audio_recordings.pm
+++ b/lib/calcms/audio_recordings.pm
@@ -23,11 +23,7 @@ sub get_columns($) {
 
     my $dbh     = db::connect($config);
     my $cols    = db::get_columns( $dbh, 'calcms_audio_recordings' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    return { map { $_ => undef } @$cols };
 }
 
 # get playout entries
diff --git a/lib/calcms/calendar.pm b/lib/calcms/calendar.pm
index 9a89b85..70be184 100644
--- a/lib/calcms/calendar.pm
+++ b/lib/calcms/calendar.pm
@@ -164,10 +164,7 @@ sub get($$) {
             exclude_locations => 1,
         }
     );
-    my $used_day = {};
-    for my $day (@$used_days) {
-        $used_day->{ $day->{start_date} } = 1;
-    }
+    my $used_day = { map { $_->{start_date} => 1 } @$used_days };
 
     for my $year ( sort { $a <=> $b } keys %$years ) {
         my $months = $years->{$year};
diff --git a/lib/calcms/comments.pm b/lib/calcms/comments.pm
index 0fc1aa7..3bcdeb0 100644
--- a/lib/calcms/comments.pm
+++ b/lib/calcms/comments.pm
@@ -390,12 +390,7 @@ sub get_events($$$$) {
     my $params = $request->{params}->{checked}->{comment};
 
     #get event_ids from comments
-    my $event_ids = {};
-    for my $comment (@$comments) {
-        my $event_id = $comment->{event_id};
-        $event_ids->{$event_id} = 1;
-    }
-
+    my $event_ids = { map { $_->{event_id} => 1 } @$comments };
     my @keys = keys %{$event_ids};
     #get events from comment's event ids
     return [] if ( scalar @keys ) == 0;
diff --git a/lib/calcms/creole_wiki.pm b/lib/calcms/creole_wiki.pm
index 8452645..1ab1406 100644
--- a/lib/calcms/creole_wiki.pm
+++ b/lib/calcms/creole_wiki.pm
@@ -191,10 +191,7 @@ sub extractMeta ($$) {
     if ( defined $comments ) {
 
         #build index for meta already defined
-        my $meta_keys = {};
-        for my $pair (@$meta) {
-            $meta_keys->{ $pair->{name} . '=' . $pair->{value} } = 1;
-        }
+        my $meta_keys = { map { $_->{name}."=".$_->{value} => 1 } @$meta };
 
         while ( $comments =~ /\~\~META\:(.+?)\=(.+?)\~\~/g ) {
             my $name  = $1;
diff --git a/lib/calcms/db.pm b/lib/calcms/db.pm
index ed2c850..97dfb99 100644
--- a/lib/calcms/db.pm
+++ b/lib/calcms/db.pm
@@ -125,11 +125,7 @@ sub get_columns_hash($$) {
     my $table = shift;
 
     my $columns = db::get_columns( $dbh, $table );
-    my $result = {};
-    for my $column (@$columns) {
-        $result->{$column} = 1;
-    }
-    return $result;
+    return { map { $_ => 1 } @$columns };
 }
 
 #returns last inserted id
diff --git a/lib/calcms/event_history.pm b/lib/calcms/event_history.pm
index 94b5524..7f9c836 100644
--- a/lib/calcms/event_history.pm
+++ b/lib/calcms/event_history.pm
@@ -16,11 +16,7 @@ sub get_columns ($){
 
     my $dbh     = db::connect($config);
     my $cols    = db::get_columns( $dbh, 'calcms_event_history' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    return { map { $_ => undef } @$cols };
 }
 
 sub get ($$){
diff --git a/lib/calcms/password_requests.pm b/lib/calcms/password_requests.pm
index 76bf2cc..376ec9d 100644
--- a/lib/calcms/password_requests.pm
+++ b/lib/calcms/password_requests.pm
@@ -23,11 +23,7 @@ sub get_columns ($) {
 
     my $dbh     = db::connect($config);
     my $cols    = db::get_columns( $dbh, 'calcms_password_requests' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    return { map { $_ => undef } @$cols };
 }
 
 sub get ($$) {
diff --git a/lib/calcms/playout.pm b/lib/calcms/playout.pm
index 40372bc..beef723 100644
--- a/lib/calcms/playout.pm
+++ b/lib/calcms/playout.pm
@@ -20,11 +20,7 @@ sub get_columns ($) {
 
     my $dbh     = db::connect($config);
     my $cols    = db::get_columns( $dbh, 'calcms_playout' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    return { map { $_ => undef } @$cols };
 }
 
 
diff --git a/lib/calcms/project.pm b/lib/calcms/project.pm
index 78dbdad..3e89d21 100644
--- a/lib/calcms/project.pm
+++ b/lib/calcms/project.pm
@@ -30,11 +30,7 @@ sub get_columns ($) {
 
     my $dbh     = db::connect($config);
     my $cols    = db::get_columns( $dbh, 'calcms_projects' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    return { map { $_ => undef } @$cols };
 }
 
 # get projects
diff --git a/lib/calcms/series.pm b/lib/calcms/series.pm
index 903e2ff..894ff38 100644
--- a/lib/calcms/series.pm
+++ b/lib/calcms/series.pm
@@ -34,11 +34,7 @@ sub get_columns ($) {
 
     my $dbh     = db::connect($config);
     my $cols    = db::get_columns( $dbh, 'calcms_series' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    return { map { $_ => undef } @$cols };
 }
 
 # get series content
@@ -772,14 +768,14 @@ sub get_images ($$) {
             series_id  => $options->{series_id}
         }
     );
-    my $images = {};
-    my $found  = 0;
-    for my $event (@$events) {
-        my $image = $event->{image};
-        $image =~ s/.*\///;
-        $images->{$image} = 1;
-        $found++;
-    }
+    my $images = { 
+        map {
+            my $image = $_->{image};
+            $image =~ s/.*\///;
+            { $image => 1 };
+        } @$events 
+    };
+    my $found  = scalar(keys %$images);
 
     return undef if $found == 0;
 
@@ -948,10 +944,7 @@ sub set_event_ids ($$$$$) {
     return unless defined $event_ids;
 
     #make lookup table from events
-    my $event_id_hash = {};
-    for my $event_id (@$event_ids) {
-        $event_id_hash->{$event_id} = 1;
-    }
+    my $event_id_hash = { map { $_ => 1 } @$event_ids };
 
     #get series_entries from db
     #my $bind_names=join(',', (map { '?' } @$event_ids));
@@ -964,16 +957,8 @@ sub set_event_ids ($$$$$) {
     my $dbh = db::connect($config);
     my $results = db::get( $dbh, $query, $bind_values );
 
-    my $found = {};
-
     #mark events found assigned to series
-    my $i = 1;
-    for my $event (@$results) {
-
-        #print "found event $i: $event->{event_id}\n";
-        $found->{ $event->{event_id} } = 1;
-        $i++;
-    }
+    my $found = { map { $_->{event_id} => 1 } @$results };
 
     #insert events from list, not found in db
     for my $event_id (@$event_ids) {
diff --git a/lib/calcms/series_dates.pm b/lib/calcms/series_dates.pm
index c8d0871..0565c7f 100644
--- a/lib/calcms/series_dates.pm
+++ b/lib/calcms/series_dates.pm
@@ -26,11 +26,7 @@ sub get_columns ($) {
 
     my $dbh     = db::connect($config);
     my $cols    = db::get_columns( $dbh, 'calcms_series_dates' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    return { map { $_ => undef } @$cols };
 }
 
 # get all series_dates for studio_id and series_id within given time range
@@ -261,12 +257,8 @@ sub addSeriesScheduleAttributes ($$) {
     my $config  = shift;
     my $entries = shift;
 
-    my $scheduleIds = {};
-
     # get series schedule ids used at entries
-    for my $entry (@$entries) {
-        $scheduleIds->{ $entry->{series_schedule_id} } = 1;
-    }
+    my $scheduleIds = { map { $_->{series_schedule_id} => 1 } @$entries };
     my @scheduleIds = keys %$scheduleIds;
     return $entries if scalar(@scheduleIds) == 0;
 
diff --git a/lib/calcms/series_events.pm b/lib/calcms/series_events.pm
index 28ccef6..1a21cf6 100644
--- a/lib/calcms/series_events.pm
+++ b/lib/calcms/series_events.pm
@@ -41,7 +41,7 @@ sub save_content($$) {
     my $config = shift;
     my $entry  = shift;
 
-    return undef unless ( defined $entry->{id} );
+    return undef unless defined $entry->{id};
 
     for my $attr ( keys %$entry ) {
         next unless defined $entry->{$attr};
@@ -308,10 +308,7 @@ sub check_permission($$) {
     delete $options->{permission};
 
     #convert check list to hash
-    my $check = {};
-    for my $permission ( @{ $options->{check_for} } ) {
-        $check->{$permission} = 1;
-    }
+    my $check = { map { $_ => 1 } @{ $options->{check_for} } };
     delete $options->{check_for};
 
     # is project assigned to studio
diff --git a/lib/calcms/series_schedule.pm b/lib/calcms/series_schedule.pm
index cc4ebac..dbcbf8d 100644
--- a/lib/calcms/series_schedule.pm
+++ b/lib/calcms/series_schedule.pm
@@ -28,11 +28,8 @@ sub get_columns ($) {
 
     my $dbh     = db::connect($config);
     my $cols    = db::get_columns( $dbh, 'calcms_series_schedule' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    return { map { $_ => undef } @$cols };
+
 }
 
 #map schedule id to id
diff --git a/lib/calcms/studio_timeslot_dates.pm b/lib/calcms/studio_timeslot_dates.pm
index 61be874..d407a02 100644
--- a/lib/calcms/studio_timeslot_dates.pm
+++ b/lib/calcms/studio_timeslot_dates.pm
@@ -22,11 +22,7 @@ sub get_columns ($){
 
     my $dbh     = db::connect($config);
     my $cols    = db::get_columns( $dbh, 'calcms_studio_timeslot_dates' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    return { map { $_ => undef } @$cols };
 }
 
 # get all studio_timeslot_dates for studio_id within given time range
diff --git a/lib/calcms/studio_timeslot_schedule.pm b/lib/calcms/studio_timeslot_schedule.pm
index 521f4d9..3198132 100644
--- a/lib/calcms/studio_timeslot_schedule.pm
+++ b/lib/calcms/studio_timeslot_schedule.pm
@@ -20,11 +20,7 @@ sub get_columns($) {
 
 	my $dbh     = db::connect($config);
 	my $cols    = db::get_columns( $dbh, 'calcms_studio_timeslot_schedule' );
-	my $columns = {};
-	for my $col (@$cols) {
-		$columns->{$col} = 1;
-	}
-	return $columns;
+    return { map { $_ => undef } @$cols };
 }
 
 #map schedule id to id
diff --git a/lib/calcms/studios.pm b/lib/calcms/studios.pm
index f9fbeca..77f05ac 100644
--- a/lib/calcms/studios.pm
+++ b/lib/calcms/studios.pm
@@ -17,11 +17,7 @@ sub get_columns($) {
 
     my $dbh     = db::connect($config);
     my $cols    = db::get_columns( $dbh, 'calcms_studios' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    return { map { $_ => undef } @$cols };
 }
 sub get($;$) {
     my $config = shift;
diff --git a/lib/calcms/user_default_studios.pm b/lib/calcms/user_default_studios.pm
index 4c96999..58d0090 100644
--- a/lib/calcms/user_default_studios.pm
+++ b/lib/calcms/user_default_studios.pm
@@ -16,13 +16,9 @@ sub debug;
 sub get_columns($) {
     my $config = shift;
 
-    my $dbh     = db::connect($config);
-    my $cols    = db::get_columns( $dbh, 'calcms_user_default_studios' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    my $dbh  = db::connect($config);
+    my $cols = db::get_columns( $dbh, 'calcms_user_default_studios' );
+    return { map { $_ => undef } @$cols };
 }
 
 sub get ($$) {
diff --git a/lib/calcms/user_sessions.pm b/lib/calcms/user_sessions.pm
index 6d1f52a..97566f3 100644
--- a/lib/calcms/user_sessions.pm
+++ b/lib/calcms/user_sessions.pm
@@ -28,11 +28,7 @@ sub get_columns($) {
 
     my $dbh     = db::connect($config);
     my $cols    = db::get_columns( $dbh, 'calcms_user_sessions' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    return { map { $_ => undef } @$cols };
 }
 
 #map schedule id to id
diff --git a/lib/calcms/user_settings.pm b/lib/calcms/user_settings.pm
index 4b9d62b..2a85de7 100644
--- a/lib/calcms/user_settings.pm
+++ b/lib/calcms/user_settings.pm
@@ -138,11 +138,7 @@ sub get_columns($) {
 
     my $dbh     = db::connect($config);
     my $cols    = db::get_columns( $dbh, 'calcms_user_settings' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    return { map { $_ => undef } @$cols };
 }
 
 sub get ($$) {
diff --git a/lib/calcms/user_stats.pm b/lib/calcms/user_stats.pm
index 1561215..54aad9e 100644
--- a/lib/calcms/user_stats.pm
+++ b/lib/calcms/user_stats.pm
@@ -15,11 +15,7 @@ sub get_columns($) {
 
     my $dbh     = db::connect($config);
     my $cols    = db::get_columns( $dbh, 'calcms_user_stats' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    return { map { $_ => undef } @$cols };
 }
 
 sub get ($$) {
@@ -205,7 +201,7 @@ sub increase ($$$) {
     return undef unless defined $options->{user};
 
     my $columns = get_columns($config);
-    return undef unless defined $columns->{$usecase};
+    return undef unless exists $columns->{$usecase};
 
     my $entries = get( $config, $options );
     if ( scalar @$entries == 0 ) {
diff --git a/lib/calcms/work_dates.pm b/lib/calcms/work_dates.pm
index 7c80b10..c46ca2b 100644
--- a/lib/calcms/work_dates.pm
+++ b/lib/calcms/work_dates.pm
@@ -26,11 +26,7 @@ sub get_columns($) {
 
     my $dbh     = db::connect($config);
     my $cols    = db::get_columns( $dbh, 'calcms_work_dates' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    return { map { $_ => undef } @$cols };
 }
 
 # get all work_dates for studio_id and schedule_id within given time range
diff --git a/lib/calcms/work_schedule.pm b/lib/calcms/work_schedule.pm
index bc0c078..51039b9 100644
--- a/lib/calcms/work_schedule.pm
+++ b/lib/calcms/work_schedule.pm
@@ -27,11 +27,7 @@ sub get_columns($) {
 
     my $dbh     = db::connect($config);
     my $cols    = db::get_columns( $dbh, 'calcms_work_schedule' );
-    my $columns = {};
-    for my $col (@$cols) {
-        $columns->{$col} = 1;
-    }
-    return $columns;
+    return { map { $_ => undef } @$cols };
 }
 
 #map schedule id to id
diff --git a/website/agenda/planung/projects.cgi b/website/agenda/planung/projects.cgi
index 2611840..2978435 100755
--- a/website/agenda/planung/projects.cgi
+++ b/website/agenda/planung/projects.cgi
@@ -237,11 +237,7 @@ sub show_projects {
         $project->{pid} = $project->{project_id};
 
         # get assigned studios by id
-        my $assigned_studio_by_id = {};
-        for my $studio (@$project_studio_assignements) {
-            $assigned_studio_by_id->{ $studio->{studio_id} } = 1;
-        }
-
+        my $assigned_studio_by_id = { map { $_->{studio_id} => 1 } @$project_studio_assignements };
         my $assigned_studios   = [];
         my $unassigned_studios = [];
         for my $studio (@$studios) {
diff --git a/website/agenda/planung/series.cgi b/website/agenda/planung/series.cgi
index 5d33a1b..0a4d695 100755
--- a/website/agenda/planung/series.cgi
+++ b/website/agenda/planung/series.cgi
@@ -333,7 +333,7 @@ sub save_series {
     # fill series entry
     my $entry = {};
     for my $param ( keys %$params ) {
-        if ( defined $columns->{$param} ) {
+        if ( exists $columns->{$param} ) {
             $entry->{$param} = $params->{$param} || '';
         }
     }