Perl Script Learning Notes Basics Tutorial

1. When chomp without parameters, the default parameters are used and the $_ operation is done.
2. Array @array ... Available $array[number] references. $ #array. Represents the number of indexes in an array.
3. $! contains error messages;
4. The default open file handle is "<" is input, ">>" and ">" The difference is a way to add the operation of the file.
if (@ARGV < 2) {
Die "Not Enough arguments\n";
}
5. Select LOG; change the default handle; You do not need to enter the handle parameter in the next output;
Print LOG "Hello world!\n";
6. Reopening a handle closes the previous file handle;
7. My @k = Keys%hash; My@v = values%hash return a key value or a variable value;
There is a key,delete function to delete key and value when exists function is judged in hask.
8. "." is the wildcard character of the metacharacters. The asterisk ("*") is the previous 0 or more times (simple quantifiers), "+" means one or more, "?" is to indicate that the occurrence does not occur once.
9. "/I" is not case-insensitive, "/s" matches any symbol, "/x" adds spaces, and "/is" is combined;
"m//" In fact represents the general pattern matching "//" can also use M (), M{},m<> Similar to "qw//".
11. The word boundary anchors, \b, is used for the word. such as/\bfred\b/can match the word Fred.
12.$1, such as the name of the same pattern, the matching of the parentheses in the logarithm of the item;
13. Three special variables ($ ', $&amp, $ ') to indicate where the matches are, respectively, to the left and right.
"/S" if not added "/g" can only be performed once;
15.unless is used on the contrary, and can form a statement immediately after the control modifier, elsif is not ElseIf, and an e is missing;
16.last and next correspond to the rest of the language and Continue;redo the next loop of the conditional expression to jump directly to the top of the loop content.
17.unlink "file"; rename "old", "new"; link "file"; mkdir "File", Oct ("permission"), rmdir "file"; chmod 0755, "Fred", " Barney "Chown $user, $group, Glob" *.O ", Utime $now, $ago, Glob" * ";
18.index.. $where = Index ($big, $small), found at the beginning, index returns 0. If one character is returned, it returns 1, followed by an analogy. If the substring does not exist, return -1;rindex ...
$part = substr ($string, $initial _position, $length);
20.my $money = sprintf "%.2f", 2.49997;
21.system "Date";
22.my (undef, $card _num, undef, undef, undef, $count) = Split/:/;