In a quick test, index doesn't seem to be quicker than simple regex. example: 

$ perl -MTime::HiRes -MBenchmark=timethese -le'open F,"</usr/share/dic
+t/words";@words=<F>;chomp for @words; $re= q(^bonjour); timethese(-1,
+ { index => sub { for (@words) { return 1 if index($_,"bonjour") != -
+1 } }, re => sub { for (@words) { return 1 if /\bbonjour\b/ } }, q(re
+^) => sub { for (@words) { return 1 if /^bonjour/ } }, re_comp => sub
+ { $re= qr/^bonjour/o; for (@words) { return 1 if /$re/o } }, grep =>
+ sub { return 1 if grep /bonjour/, @words } } )'
Benchmark: 
running
 grep, index, re, re^, re_comp
 for at least 1 CPU seconds
...

      grep:  2 wallclock secs ( 1.08 usr +  0.00 sys =  1.08 CPU) @ 32
+.41/s (n=35)

     index:  1 wallclock secs ( 1.12 usr +  0.02 sys =  1.14 CPU) @ 26
+7.54/s (n=305)

        re:  1 wallclock secs ( 1.10 usr +  0.02 sys =  1.12 CPU) @ 27
+2.32/s (n=305)

       re^:  1 wallclock secs ( 1.14 usr +  0.00 sys =  1.14 CPU) @ 32
+7.19/s (n=373)

   re_comp:  1 wallclock secs ( 1.04 usr +  0.00 sys =  1.04 CPU) @ 26
+8.27/s (n=279)

[download]
In this test anchoring the regex with '^' boost a little (+20%), and index or compiling the regex doesn't help. As you said, profiling the code can help here.

In reply to Re^2: how to speed up pattern match between two files by gnujsa
in thread how to speed up pattern match between two files by Anonymous Monk

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