Which one is good practice, a lexical filehandle or a typeglob?

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The earliest edition of the Llama Book is from 1993, before lexical filehandles were part of the Perl language. Lexical filehandles are a better practice for a variety of reasons. The most important disadvantages of typeglobs are

  1. they are always global in scope, which can lead to insidious bugs like this one:

    sub doSomething {
  my ($input) = @_;
  # let's compare $input to something we read from another file
  open(F, "<", $anotherFile);
  @F = <F>; 
  close F;
  do_some_comparison($input, @F);
}

open(F, "<", $myfile);
while (<F>) {
    doSomething($_);   # do'h -- just closed the F filehandle
}
close F;

  2. they are harder to pass to a subroutine than a lexical filehandle

    package package1;
sub log_time { # print timestamp to filehandle
    my ($fh) = @_;
    print $fh scalar localtime, "\n";
}

package package2;
open GLOB, '>', 'log1';
open $lexical, '>', 'log2';

package1::log_time($lexical);         # works as expected
package1::log_time(GLOB);             # doesn't work
package1::log_time('GLOB');           # doesn't work
package1::log_time(*GLOB);            # works
package1::log_time(package2::GLOB);   # works
package1::log_time('package2::GLOB'); # works

See also: Why is three-argument open calls with autovivified filehandles a Perl best practice?

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