use strict;
use warnings;

chomp( my @lines = do { local @ARGV = 'mongo.tab'; <> } );
my @headers = split /\t/, shift @lines;
my @records = map [ split /\t/ ], @lines;
1;

##</code><code>##

% perl -d munge.pl
Loading DB routines from perl5db.pl version 1.23
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(munge.pl:4):	chomp( my @lines = do { local @ARGV = 'mongo.tab'; <> } );
  DB<1> 

##</code><code>##

  DB<1> c 7
main::(munge.pl:7):	1;
  DB<2>

##</code><code>##

  DB<2> p scalar @records
16215
  DB<3> p scalar @headers
118
  DB<4> 

##</code><code>##

  DB<4> $h{ $_ }++ for map $_->[ 0 ], @records
  DB<5> p scalar keys %h
16215
  DB<6> 

##</code><code>##

  DB<6> $h2{ $_ }++ for map $_->[ 1 ], @records
  DB<7> p scalar keys %h2
9027

##</code><code>##

  DB<8> p ( sort { $h2{ $b } <=> $h2{ $a } } keys %h2 )[ 0 ]

  DB<9>

##</code><code>##

  DB<10> p $h2{''}
2904
  DB<11>

##</code><code>##

  DB<12> p ( sort { $h2{ $b } <=> $h2{ $a } } keys %h2 )[ 1 ]
"BBX "

##</code><code>##

my $re = qr/ *\t */;
my @headers = split /$re/, shift @lines;
my @records = map [ split /$re/ ], @lines;

##</code><code>##

  DB<13> R
Warning: some settings and command-line options may be lost!

Loading DB routines from perl5db.pl version 1.23
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(munge.pl:4):	chomp( my @lines = do { local @ARGV = 'mongo.tab'; <> } );
  DB<12>