Bizarrer perl behavior with glob [duplicate]

问题

This question already has answers here:

Why does Perl's glob return undef for every other call? (3 answers)

Closed 5 years ago.

use strict;
use warnings;
#only linux
#use diagnostics;

# - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - -
sub in_function {
    my $file = shift;

    glob($file) or die ("$file file was not found\n"); #this fails second time called

    # this is ok second time called
    #my @dummy = glob($file) or die ("$file file was not found\n");
}
# - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - -
my $file = "/tmp/file1*.pdf";
glob($file) or die ("$file file was not found\n");
in_function($file);
$file = "/tmp/file2*.pdf";
glob($file) or die ("$file file was not found\n");
in_function($file);

First glob is fine First in_function glob is fine Second glob is fine Second in_function glob fails Why do I need to assign glob to a variable when called within a function?

回答1:

From perldoc -f glob

In scalar context, glob iterates through such filename expansions, returning undef when the list is exhausted.

The following will do the trick:

() = glob($file) 
   or die ...;

But you problably want to know what the matches are, so you can use

my @matches = glob($file) 
   or die ...;

来源：https://stackoverflow.com/questions/25935585/bizarrer-perl-behavior-with-glob