use strict; use warnings; my $rhData = { 1990 => [1, 2, 3], 1991 => [2, 3, 5], 1992 => [1, 2, 7, 9], 1993 => [3, 7, 8, 13], 1994 => [1, 4, 8, 12, 17], 1995 => [2, 3, 4, 6, 7, 10, 12, 13, 14, 20], 1996 => [1, 4, 5, 8, 9, 12, 14, 16, 17, 19, 20], 1997 => [1, 2, 5, 6, 7, 10, 12, 14, 16, 17, 20], 1998 => [4, 5, 6, 7, 10, 11, 13, 14, 15, 18, 20], 1999 => [3, 5, 6, 7, 8, 9, 11, 12, 16, 19, 20] }; my $rhRevLookup = {}; foreach my $year (keys %$rhData) { $rhRevLookup->{$_}->{$year} ++ for @{$rhData->{$year}}; } my @range = (1995 .. 1999); my %frequencies = (); $frequencies{$_} ++ for map { (@{$rhData->{$_}}) } @range; my $header = q{ItemID}; $header .= qq{ $_} for @range; $header .= qq{ Freq.\n}; my $template = q{%-10d}; $template .= q{%-8s} for @range; $template .= qq{%-5d\n}; print $header; print map { sprintf $template, @$_ } map { my $raRow = []; push @$raRow, $_->[0]; foreach my $year (@range) { push @$raRow, $rhRevLookup->{$_->[0]}->{$year} ? q{=} : q{ }; } push @$raRow, $_->[1]; $raRow; } sort { $b->[1] <=> $a->[1] || $a->[0] <=> $b->[0] } map { [$_, $frequencies{$_}] } keys %frequencies;