Module code should localize any special variables it uses in each location it uses them. This is a smart and sane practice. Watch:
package MyConfigReader;
sub readConfig {
my ($file,$var) = @_;
open FILE, "< $file" or die "can't read $file: $!";
while (<FILE>) {
chomp;
my ($k,$v) = split /=/, $_, 2;
return $v if $k eq $var;
}
close FILE;
return;
}
That looks innocent, right? Watch it get blown to hell:
use MyConfigReader;
$/ = "not gonna happen";
MyConfigReader::readConfig("whatever.dat");
My program has just modified the
input record separator variable. The module relied on that being
\n, and now it isn't.
sub readConfig {
my ($file,$var) = @_;
local ($_, $/);
$/ = "\n";
# rest of function
}
So yes, this is something you should be doing. Trusting the user is potentially silly. Perhaps there should be a switch like
-T that catches blind use of "true globals" like you demonstrated.
japhy --
Perl and Regex Hacker
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