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In the second edition of his book, Friedl drily announces that readers of the first edition need not worry any longer about the /i modifier, since the issue has been already fixed.

Here is a test, showing that the difference, if any, is rather small. Getting less than 0.20 sec difference with ten thousand iterations on a one-million-char string, I would choose the /i modifier any time.

It all depends on your version of Perl and your machine speed, but if you have a recent release of both, you can safely use the /i modifier without losing much sleep.

#!/usr/bin/perl -w use strict; use Benchmark qw(timethese); for my $size (10_000, 100_000, 1_000_000) { my $string = 'a' x $size . ' While '; print "string size $size\n", ; my $x; timethese(10_000, { i_modifier => sub { $x = 1 if $string =~ m/\bwhile\b/i; }, char_class => sub { $x = 1 if $string =~ m/\b[Ww][Hh][Ii][Ll][Ee]\b/; } }); } __END__ Perl 5.6.1 ========== string size 10000 Benchmark: timing 10000 iterations of char_class, i_modifier... char_class: 1 wallclock secs ( 0.62 usr + 0.00 sys = 0.62 CPU) i_modifier: 1 wallclock secs ( 0.62 usr + 0.00 sys = 0.62 CPU) string size 100000 Benchmark: timing 10000 iterations of char_class, i_modifier... char_class: 6 wallclock secs ( 6.05 usr + 0.01 sys = 6.06 CPU) i_modifier: 6 wallclock secs ( 6.05 usr + 0.01 sys = 6.06 CPU) string size 1000000 Benchmark: timing 10000 iterations of char_class, i_modifier... char_class: 64 wallclock secs (62.17 usr + 0.31 sys = 62.48 CPU) i_modifier: 63 wallclock secs (61.87 usr + 0.25 sys = 62.12 CPU) ActiveState Perl 5.8.0 (optimized for Pentium architecture) =========================================================== string size 10000 Benchmark: timing 10000 iterations of char_class, i_modifier... char_class: 1 wallclock secs ( 0.51 usr + 0.00 sys = 0.51 CPU) i_modifier: 1 wallclock secs ( 0.52 usr + 0.00 sys = 0.52 CPU) string size 100000 Benchmark: timing 10000 iterations of char_class, i_modifier... char_class: 5 wallclock secs ( 5.12 usr + 0.02 sys = 5.14 CPU) i_modifier: 5 wallclock secs ( 5.23 usr + 0.02 sys = 5.25 CPU) string size 1000000 Benchmark: timing 10000 iterations of char_class, i_modifier... char_class: 51 wallclock secs (50.74 usr + 0.15 sys = 50.89 CPU) i_modifier: 51 wallclock secs (50.91 usr + 0.15 sys = 51.06 CPU)

In reply to Re: Re: Case in regular expressions by dbwiz
in thread Case in regular expressions by RolandGunslinger

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