use warnings; use strict; use Data::Dump qw/ dd pp /; my %h = ( 1 => [2..7], 8 => [ 9 ], 9 => [ 8 ], (map { $_ => [ 1 ] } 2..7), ); dd \%h; while ( my ($k,$v) = each %h ) { print "Loop from ",pp($k)," -> ",pp($v),"\n"; rec_delete( \%h, $k ); } dd \%h; sub rec_delete { my ($hash, $key) = @_; return unless exists $hash->{$key}; my $value = delete $hash->{$key}; keys %$hash; return unless $value; print "Recursing ",pp($key)," -> ",pp($value),"\n"; rec_delete( $hash, $_ ) for @$value; }