Perl/Basics/User Defined Functions

A function is defined by the programmer to create re-usable code. In our example, we will make an is_integer function that returns either 1 or undef depending on whether the scalar passed is an integer or not.

sub is_integer { my $scalar = shift; return 1 if (int($scalar) == $scalar); return undef; }

Usage:

print "This scalar is an integer.\n" if (defined is_integer($scalar)) else print "This is not an integer.\n";

Perl's return function can return multiple data types and variables, i.e.:

return($scalar,@array);

To use this type of function:

my ($scalar,@array) = function();