#      %   Header
 1:  81.96  NAME
 2:  79.75  DESCRIPTION
 3:  74.54  SYNOPSIS
 4:  60.26  SEE ALSO
 5:  25.86  STANDARD OPTIONS
 6:  24.25  KEYWORDS
 7:  22.32  AUTHOR
 8:  19.04  ARGUMENTS
 9:  15.88  OPTIONS
10:  15.74  BUGS
11:  11.62  CONFORMING TO
12:  11.60  FILES
13:  11.48  RETURN VALUE
14:   9.58  ERRORS
15:   8.25  NOTES
16:   5.66  COPYRIGHT
17:   4.80  ACKNOWLEDGEMENTS
18:   4.61  AUTHORS
19:   4.06  EXAMPLES
20:   3.61  ENVIRONMENT
21:   3.26  REPORTING BUGS
22:   2.23  DIAGNOSTICS
23:   2.14  EXAMPLE
24:   2.09  HISTORY
25:   2.02  INTRODUCTION
26:   1.85  VERSION
27:   1.21  CONFIGURATION
28:   1.19  AVAILABILITY
29:   1.16  WIDGET-SPECIFIC OPTIONS
30:   1.14  NOTE
Total files: 4207.

##</code><code>##

#!/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__