use strict;
use warnings;
use Data::Dumper;

my %table;
my @header = split /\s+/, scalar( <DATA> );
chomp $header[-1];

while ( my $line = <DATA> ) {
    chomp $line;
    my @fields = split /\s+/, $line;
    for my $col ( $[ .. $#header ) {
        push @{ $table{$header[$col]} }, $fields[$col];
    }
}

print Dumper \%table;

__DATA__
A   B   C   D
1   a   3   abc
4   b   4.5 xyz
3   2c  9   df