#!/usr/bin/perl -w

my $str1 = "train times tomorrow xyz";
my $str2 = "train times to xyz";
my $str3 = "train times from xyz";
my $str4 = "train times defrom xyz";
my $str5 = "train times fromar xyz";
my $str6 = "train times from";
my $str7 = "train from somewhere";

if($str1 !~ /^(\w+)?\s+(\w+)?\s+(to|from)([^\w]|\z)/) {
  print "does not match. Now we can do something\n";
}