#! perl -slw
use strict;
use G; ## Expands wildcards arguments as would be done by most *nix shells.

our $INDEX ||= 'words.index';

my %index;
if( -e $INDEX ) {
	open INDEX, '<', $INDEX or die "$INDEX: $!";
	m[^([^:]+):(\d+)$] and $index{ $1 } = $2 while <INDEX>;
	close INDEX;
}

while( my $file = @ARGV ) {
	open FILE, '<', $file or warn "$file:$!" and next;
	while( <FILE> ) {
		$index{ $_ }++ for split ' ';
	}
	close $file;
}

my( $key, $val );
open INDEX, '>', $INDEX or die "$INDEX : $!";
print INDEX "$key:$val" while ( $key, $val ) = each %index;
close INDEX;