#!/usr/bin/perl -l

# file storing all legitimate words, one per line
my $DICT = qq(/usr/share/dict/words);

# terms to test for validity
my @TEST = qw(
pizzamilkshake perlmonks pearlmonks hellothere
heytherebaby hey123 timexyz whereangelsare
);

# build dict hash
my %WORDS;
open DICT, "< $DICT" or die $!;
while (<DICT>){
    chomp;            # chop off whitespace if it's there
    $WORDS{uc $_}++;    # force UC, add key to %WORDS
}
close DICT;

my (@subs, $giveup, $p1, $p2, $sub);

for my $test (@TEST){

    $test = uc $test;        # force word to UC at the beginning
    @subs = ();            # reset sub-match array
    $giveup = $p1 = $p2 = 0;    # not giving up, starting at the start

    while (
        !$giveup &&        # else we've thrown in the towel
        $p1 < length($test)    # else found match
    ){

        $p1++;
        $sub = substr $test, $p2, $p1-$p2;    # grab next substring
        #print STDERR "sub: $sub";

        if ($WORDS{$sub}){    # if it matches a legal word...
            #print STDERR "MATCH ($sub) in $test";
            push @subs, [ $p1, $p2 ];    # successful path, save it
            $p2 = $p1;    # advance p2 to the end of the current match
        } elsif ($p1 >= length($test)){ # at the end of the string wit
+h no match
            # if the entire string doesn't match a word or we have now
+here to
            # backtrack...
            if ($p2 == 0 || @subs == 0){
                #print STDERR "giving up on $test";
                $giveup++; # nowhere to go
            } else {
                #print STDERR "backtracking...";
                # reset p1 and p2 to last state and try to get a longe
+r match
                ($p1, $p2) = @{$subs[$#subs]};    
                pop @subs; # delete last item... it's path is a dead e
+nd
            }
        }
    }
    print ("$test: " . ($giveup ? "NO" : "YES"));
}


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