Perl 의 file open 함수

http://perldoc.perl.org/functions/open.html
→ mode에 대해 잘 나와 있음.
예)

 open(my $fh, "<", "input.txt") or die "cannot open < input.txt: $!";  
 open(my $fh, ">", "output.txt") or die "cannot open > output.txt: $!";  
 open(my $fh, "<:encoding(UTF-8)", "filename") || die "can't open UTF-8 encoded filename: $!";  
 open(my $tmp, "+>", undef) or die ...  
 open($fh, ">", \$variable) || ..