So i was tracking down a bug in a module i wrote (which ended up being a non-closed file handle) and i noticed this. Take the following code:

#!/usr/bin/perl -wT
use strict;
sub foo {
        open(FOO, '>/tmp/foo') or die "$!\n";
        print FOO "this is a test\n";
}
sub bar {
        open (BAR, '/tmp/foo') or die "$!\n";
        while (<BAR>) {
        print;
        }
}
foo();
bar();
[download]

This code produces no output untill i add a close FOO; in &foo. However, the following code does work:

#!/usr/bin/perl -Tw
use strict;
sub foo {
        open(FOO, '/tmp/foo') or die "$!\n";
        while (<FOO>) {
                print;
        }
}
sub bar {
        open (BAR, '/tmp/foo') or die "$!\n";
        while (<BAR>) {
        print;
        }
}
foo();
bar();
[download]

So what's going on here? Why can't I open the same file with two different modes when I can open the same file in the same mode? And why doesn't the second open barf? I tried this in linux under both 5.00053 and 5.6 and got the same results.

BlueLines

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