I just found out the time taken by a string assignment is not constant for a given argument. It's dependent on the previous state of the variable to which the string is assigned.

In your test, the time taken by $_ = '|0|0|0|0|0|0|'; is not constant because the previous state of $_ isn't constant. That means you aren't testing what you think you are testing. Using a lexical instead of $_ solves that problem.

Your tests really shouldn't be in subs either. They add a serious overhead, especially since your data is so small. 

use strict;
use warnings;

use Benchmark qw( cmpthese );

my %tests = (
   subst       => '$x =~ s/.//;',
   substr_lval => 'substr($x,0,1) = "";',
   substr_mod  => 'substr($x,0,1,"");',
   reverse     => '$x = reverse $x; chop($x); $x = reverse($x);',
   substr_copy => '$x = substr($x,1);',
);

for (values %tests) {
   $_ = 'use strict; use warnings; my $x = "|0|0|0|0|0|0|"; ' . $_;
}

cmpthese(-5, \%tests);

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In reply to Re: Ways to delete start of string by ikegami
in thread Ways to delete start of string by hsmyers

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