learning Perl：91行有啥用？ 88 print " ----------------------------------_matching_multiple-line_text-------------------------- "; 91 my $lines = join '', <FILE>;

 89 open FILE, "< file_4_ex_ch7.txt"
     90     or die "cannot open file: $!";
     91 my $lines = join '', <FILE>;
     92 print $lines." ";
     93 $lines =~ s/^/file_4_ex_ch7.txt: /gm;
     94 print $lines;

----------------------------------_matching_multiple-line_text--------------------------
anonymous attribute demolition grammar rules indices refernces lignA
Align,

ligning.
.
AABB

file_4_ex_ch7.txt: anonymous attribute demolition grammar rules indices refernces lignA
file_4_ex_ch7.txt: Align,
file_4_ex_ch7.txt:
file_4_ex_ch7.txt: ligning.
file_4_ex_ch7.txt: .
file_4_ex_ch7.txt: AABB

----------------------------------_matching_multiple-line_text--------------------------

----------------------------------_--------------------------
bash-2.03$ cat file_4_ex_ch7.txt
anonymous attribute demolition grammar rules indices refernces lignA
Align,

ligning.
.
AABB
bash-2.03$