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Perl/Basics/User Defined Functions

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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;


print "This scalar is an integer.\n" if (defined is_integer($scalar)) else print "This is not an integer.\n";
Perl's return function can return multiple data types and variables, i.e.:
To use this type of function:
my ($scalar,@array) = function();