#!/usr/bin/perl

#  igf -c5 <file>
#
#  Insert blank line before lines containing
#  a value in column <col> that differs from 
#  value in previous line.
#

use Getopt::Std;

getopts ("c:");

$opt_c = 0 unless defined $opt_c;
$opt_c--;

while (<>) {
@F=split;
print "\n" if $a ne $F[$opt_c]; 
print; 
$a=$F[$opt_c];
}
