perl usage...
Perl, also Practical Extraction and Report Language (a backronym, see below) is a dynamic procedural programming language designed by Larry Wall and first released in 1987. Perl borrows features from C, shell scripting (sh), AWK, sed, Lisp, and, to a lesser extent, many other programming languages.
The overall structure of Perl derives broadly from the programming language C. Perl is a procedural programming language, with variables, expressions, assignment statements, brace-delimited code blocks, control structures, and subroutines.
Perl also takes features from shell programming. All variables are marked with leading sigils. Sigils unambiguously identify variable names, allowing Perl to have a rich syntax. Importantly, sigils allow variables to be interpolated directly into strings. Like the Unix shells, Perl has many built-in functions for common tasks, like sorting, and for accessing system facilities.
Perl takes lists from Lisp, associative arrays from AWK, and regular expressions from sed. These simplify and facilitate all manner of parsing, text handling, and data management tasks.
In Perl 5, features were added that support complex data structures, first-class functions (i.e. closures as values), and an object-oriented programming model. These include references, packages, and class-based method dispatch. Perl 5 also saw the introduction of lexically scoped variables, which make it easier to write robust code, and modules, which make it practical to write and distribute libraries of Perl code.
All versions of Perl do automatic data typing and memory management. The interpreter knows the type and storage requirements of every data object in the program; it allocates and frees storage for them as necessary. Legal type conversions are done automatically at run time; illegal type conversions are fatal errors.
Perl is widely used in finance and bioinformatics, where it is valued for rapid application development, ability to handle large data sets, and the availability of many standard and third-party modules.