#! perl -slw
use strict;
use Benchmark qw[ cmpthese ];

our $words = do{ local( @ARGV, $/ ) = 'words.txt'; <> }; close $ARGV;
our @words = split ' ', $words;
our %words;
@words{ do{
    my $word = $_;
    map{
        my $copy;
        substr( $copy = $word, $_, 1, '.' );
        $copy;
    } 0 .. length() -1
}} = ($_) x ( length() -1 ) for @words;

our $N //= 3;
our $P //= 0.01;
our @toLookFor = map {
    rand() > $P ? ()
        :  do {
            my $w = $_;
            my $p = int( rand length()-1 );
            $w =~ s[.{$p}\K.][.];
            $w;
        };
} @words;

printf "Looking for %d terms amongst %d words\n",
    scalar @toLookFor, scalar @words;

cmpthese $N, {
    a => q[
        for my $re ( @toLookFor ) {
             m[^$re$]
             #and print "a:$re :: $_"
             for @words;
        }
    ],
    b => q[
        $words =~ m[\b($_)\b]
            #and print "b:$_ :: $1"
            for @toLookFor;
    ],
    c => q[
        # print
        $words{ $_ } or 1 for @toLookFor;
    ],
}

__END__
C:\test>junk42 -P=0.02
Looking for 3651 terms amongst 178691 words

     s/iter                     a                     b                     c
a       167                    --                  -95%                 -100%
b      8.20                 1931%                    --                 -100%
c 1.00e-015 16662499999999995902%   820299999999997696%                    --