Perl :Interchangeability of Strings and Numeric Value

$string = "43";
$number = 28;
$result = $string + $number;

Result :71

$number = <STDIN>;
chop ($number);
$result = $number + 1;


if $number =22\n
than first chop function will convert the string to integer =22 and mathematical  operation will perform

If a string contains characters that are not digits, the string is
converted to 0 when used in an integer context. For example:
$result = "hello" * 5;
# this assigns 0 to $result, since "hello"
becomes 0
This is true even if the string is a valid hexadecimal integer if the
quotes are removed, as in the following:
$result = "0xff" + 1;
In cases like this, Perl does not tell you that anything has gone
wrong, and your results might not be what you expect.
Also, strings containing misprints might not contain what you
expect. For example:
$result = "12O34"; # the letter O, not the
number 0
When converting from a string to an integer, Perl starts at the left
and continues until it sees a letter that is not a digit. In the
preceding instance, 12O34 is converted to the integer 12, not
12034
Initial Values