Use @h{@a} = () instead of undef @h{@a}

as it works even when @a is empty.

3 files changed, 4 insertions, 4 deletions

diff --git a/challenge-009/e-choroba/perl5/ch-1.pl b/challenge-009/e-choroba/perl5/ch-1.pl
index 4a74e71fe3..561873482a 100644..100755
--- a/challenge-009/e-choroba/perl5/ch-1.pl
+++ b/challenge-009/e-choroba/perl5/ch-1.pl
@@ -6,7 +6,7 @@ use feature qw{ say };
 sub distinct_digits {
     my ($n) = @_;
     my %d;
-    undef @d{split //, $n};
+    @d{split //, $n} = ();
     return keys %d
 }
 
diff --git a/challenge-057/e-choroba/perl/Tree.pm b/challenge-057/e-choroba/perl/Tree.pm
index a0a4a8a51f..176c5f574a 100644
--- a/challenge-057/e-choroba/perl/Tree.pm
+++ b/challenge-057/e-choroba/perl/Tree.pm
@@ -28,7 +28,7 @@ sub from_edges {
         push @children, $child;
     }
     my %root;
-    undef @root{ keys %tree };
+    @root{ keys %tree } = ();
     delete @root{ @children };
     my @roots = keys %root;
     die "One root not found: @roots." if @roots != 1;
diff --git a/challenge-060/e-choroba/perl/ch-2.pl b/challenge-060/e-choroba/perl/ch-2.pl
index 0894531600..438c4e5954 100755
--- a/challenge-060/e-choroba/perl/ch-2.pl
+++ b/challenge-060/e-choroba/perl/ch-2.pl
@@ -5,7 +5,7 @@ use strict;
 sub extend {
     my ($length, $short, $long) = @_;
     my %next;
-    undef @next{@$short};
+    @next{@$short} = ();
     for my $i (0 .. $#$short) {
         for my $j (0 .. $#$short) {
             my $new = 0 + ($short->[$i] . $short->[$j]);
@@ -25,7 +25,7 @@ sub extend {
 sub find {
     my ($length, $greater, @list) = @_;
     my @long = grep $length == length $_, @list;
-    my %long; undef @long{@long} if @long;
+    my %long; @long{@long} = ();
     return grep $greater > $_,
            extend($length, \@list, \%long);
 }