The substr operator can be used to split or cut a string into pieces. For example, let's say you have a variable that contains the text HelloWorld.

my $string = "Hello World";

substr can be used to cut this string into pieces. In this example, character 1 (the H in Hello) will be replaced with the letter A.

substr($string, 0, 1) = "A";

In this example, the $greeting variable will contain the text "Hello" and the $planet variable will contain the text "World".

• In the $greeting variable, 0 means "start at the beginning of the string" and 5 means "get five characters".
• In the $planet variable, 0 means "start at the fifth character of the string" and 5 means "get five characters".

my $greeting = substr $string, 0, 5;
my $planet   = substr $string, 5, 5;