#!/usr/bin/perl

use strict;  
use warnings;

my $mandir = "/usr/share/man";

my %headers;  
my $count = 0;

sub peek {
    my $file = shift;
    open my $fh => "gunzip -c $file |" or die "open $file: $!";
    while (<$fh>) {
        next unless /^\.SH\s*(.*)/;
        my $header = $1;
           $header =~ s/\s+$//;
           $header =~ s/^"(.*)"\s*$/$1/;
        $headers {$header} ++;
    }
    close $fh;
    $count ++;
}

foreach my $file (<$mandir/*/*.?.gz>) {
    next if -l $file;
    peek $file;
}

my $i = 0;
print " #      %   Header\n";
foreach my $header (sort {$headers {$b} <=> $headers {$a}} keys %headers) {
    last if 1 > (my $perc = 100 * $headers {$header} / $count);
    printf "%2d: %6.2f  %s\n" => ++ $i, $perc, $header;
}

print "Total files: $count.\n";

__END__