The most basic type of variable in Perl is the scalar variable. Scalar variables hold strings and numbers both, and are remarkable as the strings and numbers are completely interchangable.

More interesting kind of variables in perl is the array variable which are nothing but a list of scalars entities (i'e numbers and strings). Array variables do have the same format as that of a scalar variables except that they are prefixed by a symbol @.

In PERL files are given a name, also called handle. All the input and output of the file is achieved by filehandling functions. Filehandles are also a means to communicate from one program to another program.

Perl is an iterative programing language in which the control flows from first statement of the program to the last statement until and unless something interrupts. The things that can interrupt the linear flow are called conditional branches and loop structures.

The most useful features of Perl among many is its powerful string manipulation functions. At the heart of this comes the regular expression (RE) which is shared among many other utilities in UNIX.