my $q1s = join('|', @matchwords);
my $q1  = qr/$q1s\s*\w+/;

my $q3s = join('|', @matchwords);
my $q3  = qr/($q3s)\\s*\\w+/;

##</code><code>##

alternation, grouping:  1 wallclock secs ( 0.58 usr +  0.00 sys =  0.58 CPU) @ 1724137.93/s (n=1000000)
alternation, no grouping:  5 wallclock secs ( 4.85 usr +  0.00 sys =  4.85 CPU) @ 206185.57/s (n=1000000)
loop, grouping: 24 wallclock secs (23.33 usr +  0.00 sys = 23.33 CPU) @ 42863.27/s (n=1000000)
loop, no grouping: 23 wallclock secs (22.57 usr +  0.00 sys = 22.57 CPU) @ 44306.60/s (n=1000000)