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读取文件的简单程序报错了求指点

时间：2010-10-06

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use strict;
use warnings;
main(@ARGV);
sub main
{
my $line;
open FH,"short.txt";
while ($line=<FH>){
print if($line =~ m|/|);
}
close FH;
}
sub message
{
my $m=shift or return;
print "$m\n";
}

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cat short.txt

This page describes the syntax of regular expressions in Perl.
If you haven't used regular expressions before, a quick-start
introduction is available in perlrequick, and a longer tutorial
introduction is available in perlretut.
For reference on how regular expressions are used in matching
operations, plus various examples of the same, see discussions of "m//",
"s///", "qr//" and "??" in "Regexp Quote-Like Operators" in perlop.
Matching operations can have various modifiers. Modifiers that relate to
the interpretation of the regular expression inside are listed below.
Modifiers that alter the way a regular expression is used by Perl are
detailed in "Regexp Quote-Like Operators" in perlop and "Gory details of
parsing quoted constructs" in perlop.

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perl -w readshort.pl
Use of uninitialized value in print at readshort.pl line 31, <FH> line 8.
Use of uninitialized value in print at readshort.pl line 31, <FH> line 9.

如果用$_就没事

use strict;
use warnings;
main(@ARGV);
sub main
{
my $line;
open FH,"short.txt";
while ($_=<FH>){
print if($_ =~ m|/|);
}
close FH;
}
sub message
{
my $m=shift or return;
print "$m\n";
}
#END

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perl -w readshort.pl
operations, plus various examples of the same, see discussions of "m//",
"s///", "qr//" and "??" in "Regexp Quote-Like Operators" in perlop.

作者: laohuanggua 发布时间: 2010-10-06

因为 while(<FH>) {} 等于 while (my $_ = <FH>) {}
要问为什么我估计是搞 Perl 那帮家伙太懒了，想少打几个字符，对于默认 $_ 为参数的函数也会很方便。而且以前 $_ 是不能 my 的

作者: zhlong8 发布时间: 2010-10-06