Programming Perl, 4th Edition

String Operators

There is also an “addition” operator for strings that performs concatenation (that is, joining strings end to end). Unlike some languages that confuse this with numeric addition, Perl defines a separate operator (.) for string concatenation:

$a = 123;
$b = 456;
say $a + $b;     # prints 579
say $a . $b;     # prints 123456

There’s also a “multiply” operator for strings, called the repeat operator. Again, it’s a separate operator (x) to keep it distinct from numeric multiplication:

$a = 123;
$b = 3;
say $a * $b;     # prints 369
say $a x $b;     # prints 123123123

These string operators bind as tightly as their corresponding arithmetic operators. The repeat operator is a bit unusual in taking a string for its left argument but a number for its right argument. Note also how Perl is automatically converting from numbers to strings. You could have put all the literal numbers above in quotes, and it would still have produced the same output. Internally, though, it would have been converting in the opposite direction (that is, from strings to numbers).

A couple more things to think about. String concatenation is also implied by the interpolation that happens in double-quoted strings. And when you print out a list of values, you’re also effectively concatenating strings. So the following three statements produce the same output:

say $a . " is equal to " . $b . ".";    # dot operator
say $a, " is equal to ", $b, ".";       # list
say "$a is equal to $b.";               # interpolation

Which of these you use in any ...