Functions, though, work much more quickly and don't need to be tipped. Perl comes with many, many functions built-in. These functions range widely in use, from manipulating numbers and strings to working with files on disk. Some functions are used inside of larger expressions while others can stand alone.
Many functions can be any of the above.
Consider the humble lc function. Although chop can be used standalone, that doesn't mean it doesn't return any information. In fact, if used in an expression, chop returns the character that it severed off the original string. Typically there is no need to save the hacked off part of the string, which is why chop is commonly used without being part of a larger expression. Functions don't necessarily have to accept their parameters inside parentheses.