Re: Difference between this array assignment and push

One difference is that the first creates a smaller array. This is because the $1 variable is special and carries a little extra special data with it. When you stuff it into an array, that stuff stays. (I remember this fact without remembering the details. Perhaps a monk more familiar with Perl internals could explain better.)

use Data::Dumper;
use Devel::Size qw(total_size);

my $bigfoo = 'foo' x 1_000;
my @assigned = $bigfoo =~ /(foo)/g;
my @pushed;
push @pushed, $1 while $bigfoo =~ /(foo)/g;

printf "pushed:   %d\n", total_size( \@pushed );
printf "assigned: %d\n", total_size( \@assigned );

if ( Dumper( \@pushed ) eq Dumper( \@assigned ) ) {
    print "They look the same.\n";
}
else {
    print "They look different.\n";
}
__END__
pushed:   52132
assigned: 32052
They look the same.
[download]

The effect is lessened if you push @pushed, "$1":

pushed:   32132
assigned: 32052
[download]

Even then @pushed still comes out larger, probably because it started small and grew through the loop while @assigned was the right size to begin with.

My guess would be that the assigned method is faster too (especially with the repeated calls to $mech->content), but I haven't tested that.

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Re^2: Difference between this array assignment and push by xhunter (Sexton) on May 16, 2007 at 17:48 UTC
The following benchmark concurs with the idea that "Assign" is faster than "Push" for this example. `use Benchmark qw(:all) ; my $count = 1000; my $foobar = 'foobar' x 1000; timethese($count, { 'Assigned' => sub { my @assigned = $foobar =~ /(foo)/g;}, 'Pushed' => sub { my @pushed; push @pushed, $1 while $foobar =~ /( +foo)/g; }, });` [download] Benchmark Results: `Benchmark: timing 1000 iterations of Assigned, Pushed... Assigned: 1 wallclock secs ( 0.80 usr + 0.00 sys = 0.80 CPU) @ 12 +50.00/s (n=1000) Pushed: 1 wallclock secs ( 0.93 usr + 0.00 sys = 0.93 CPU) @ 10 +75.27/s (n=1000)` [download]	[reply] [d/l] [select]
Re^2: Difference between this array assignment and push by naikonta (Curate) on May 16, 2007 at 14:59 UTC
Interesting analysis, and facts on `$1` give me new lesson. I know that `$1` and friends are special, but that's it. With the context provided, I obviously prefer the assignment technique. The only reason I would go with push and while is perhaps, if I needed to check `$1` againsts some condition prior to deciding to push it to the target array. Open source softwares? Share and enjoy. Make profit from them if you can. Yet, share and enjoy!	[reply] [d/l] [select]