Nelson R. Pardee wrote:
> I want to test for the existence of a module, and do alternative
> calculations based on the result. So I have written the following, based
> on http://www.unix.org.ua/orelly/perl/cookbook/ch12_03.htm
>
> BEGIN {
> $flag_hires=0;
> unless (eval "use Time::HiRes qw(gettimeofday tv_interval)" ) {
> $flag_hires=1;
> $timefirst=$timelast = [gettimeofday];print "Hello2 ";
> }else{$timefirst=$timelast=time();print "Hello3 ";}
> }
>
> This code ALWAYS returns flag_hires=1
> even if I introduce an error, e.g., "use Time::HHiRes...."
> Why? Also, it appears I can't use [gettimeofday] in the BEGIN block.
> Thanks for your help as I delve into new areas.
Try this:
use strict;
use warnings;
my $use_hires;
my $start_time;
BEGIN {
eval "use Time::HiRes qw(gettimeofday tv_interval)";
if ($@) {
$use_hires = 0;
$start_time = time;
print "No HiRes available\n";
} else {
$use_hires = 1;
$start_time = [&gettimeofday ()];
print "HiRes available\n";
}
}
sleep 2; # something to time
if ($use_hires) {
printf "hires: %.3f seconds\n", tv_interval ($start_time);
} else {
printf "basic: %u seconds\n", time - $start_time;
}
__END__
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