Perl字符串函数 - 连接子字符串和分割

2013年3月31日 by David Farrell

Perl有许多字符串函数，让我们来看看其中一些最常用的：连接、子字符串和分割。

连接

通过在字符串之间插入句号(.)运算符来连接字符串。Perl会自动将初始化为数字的标量变量转换为字符串。

# declare and concatenate two strings
my $joke = 'A horse walks ' . 'into a bar.'; # A horse walks into a bar.
# Concatenate two scalars
my $meat  = 'ham';
my $bread = 'sandwich';
my $lunch = $meat . $bread; # hamsandwich

# Concatenate scalars initialised as numbers
my $hour        = 6;
my $minutes     = 30;
my $time_string = $hour . ':' . $minutes; # 6:30

子字符串

子字符串提取并返回现有字符串的子集。它最多接受四个参数：要提取子字符串的表达式、从何处开始提取子字符串的偏移量、子字符串的长度以及替换字符串。如果省略长度，则子字符串将运行到输入表达式的末尾。

# substr(expression, offset, [length], [replacement])
my $joke            = 'A horse walks into a bar.';
my $animal          = substr($joke, 2, 5); # horse
my $favourite_place = substr($joke, -4); # bar.

# Extract a substring and replace the substring in the original string
my $verb        = substr($joke, 8, 5, 'runs'); # walks
print $joke; # A horse runs into a bar.

关于substr的perldoc页面有更多有用的示例。

分割

split函数使用分割模式和（可选的）分割字段数限制将输入字符串分割成一系列子字符串。如果省略输入表达式，Perl将使用$_。

# split(pattern, [expression], [number_of_fields])
my $sentence       = 'A horse walks into a bar.';
my @words          = split(' ', $sentence); # A,horse,walks,into,a,bar

my $fullname       = 'Mr Stephen Doyle';

# Limit the split to two fields
my @title_and_name = split(' ', $fullname, 2); # Mr,Stephen Doyle