[EMAIL PROTECTED] (Stas Bekman) wrote:
>A combination of C<strict> and C<vars> pragmas keeps modules clean and
>reduces a bit of noise. However, the C<vars> pragma also creates
>aliases, as does C<Exporter>, which eat up more memory. When
>possible, try to use fully qualified names instead of C<use vars>.
I have to disagree with this benchmark. The aliases take up only the
tiniest bit of memory, much less than your benchmark seems to indicate.
What your benchmark shows is the code size of the 'vars.pm' module
itself, not the memory cost of making aliases. Observe:
-------Code:------------------------------------------------------------
package MyPackage;
use strict;
use vars;
@MyPackage::ISA = qw(CGI);
$MyPackage::VERSION = "1.00";
system "ps -lp $$";
-------Output:---------------
USER PID %CPU %MEM VSZ RSS TTY S STARTED TIME COMMAND
ken 59972 0.0 0.1 3.37M 696K pts/4 S + 19:50:10 0:00.14 ./vars.pl
-------Code:------------------------------------------------------------
package MyPackage;
use strict;
use vars qw(@ISA $VERSION);
@MyPackage::ISA = qw(CGI);
$MyPackage::VERSION = "1.00";
system "ps u -p $$";
-------Output:---------------
USER PID %CPU %MEM VSZ RSS TTY S STARTED TIME COMMAND
ken 54842 0.0 0.1 3.37M 696K pts/4 S + 19:50:39 0:00.13 ./vars.pl
-------Code:------------------------------------------------------------
package MyPackage;
use strict;
use vars qw(@ISA $VERSION);
@ISA = qw(CGI);
$VERSION = "1.00";
system "ps u -p $$";
-------Output:---------------
USER PID %CPU %MEM VSZ RSS TTY S STARTED TIME COMMAND
ken 58422 0.0 0.1 3.37M 696K pts/4 S + 19:52:07 0:00.13 ./vars.pl
------------------------------------------------------------------------
(This is using 5.004_04, I didn't have GTop.pm available for fine
resolution of memory.)
So there's no visible difference. Since some module somewhere in your
processes will be certain to 'use vars', you don't get any real benefit
from leaving it out in one place, and you increase the chances of making
typos.
To confirm, a couple of one-liners:
[~/bin/test],7:56pm% perl -mvars -e 'system "ps u -p $$"'
USER PID %CPU %MEM VSZ RSS TTY S STARTED TIME COMMAND
ken 79047 0.0 0.1 3.34M 680K pts/4 S + 19:57:23 0:00.13 perl -mvars -e
system "ps u -p $$"
[~/bin/test],7:57pm% perl -e 'system "ps u -p $$"'
USER PID %CPU %MEM VSZ RSS TTY S STARTED TIME COMMAND
ken 55275 0.0 0.1 3.00M 336K pts/4 S + 19:57:39 0:00.06 perl -e system "ps
u -p $$"
------------------- -------------------
Ken Williams Last Bastion of Euclidity
[EMAIL PROTECTED] The Math Forum
