#!/usr/bin/perl -w
use strict;

my $string = "firstfield second field KNOWNWORD alwaysOneWord then one or more make the last field";

my $field1 = ( split / /, $string)[0];
my $field2 = substr($string, length("$field1 "), index($string, "KNOWNWORD") - length("$field1 "));
my @temp = split / /, substr($string,  index($string, "KNOWNWORD")+length("KNOWNWORD"));
my $field3 = $temp[1];
my $field4 = join ' ', @temp[2..$#temp];

print "field1: $field1\n";
print "field2: $field2\n";
print "field3: $field3\n";
print "field4: $field4\n";