From a regular-expression point of view in Perl, there is no difference between the following two expressions except that the former is slightly clearer.$string =~ /(\S+)\s+(\S+)/; and $string =~ /\S+\s+\S+/;However, the benefit of grouping is that it allows us to extract a sequence from a regular expression. Groupings are returned ... Read More

Matching Boundaries in PerlThe \b matches at any word boundary in Perl, as defined by the difference between the \w class and the \W class. Because \w includes the characters for a word, and \W the opposite, this normally means the termination of a word. The \B assertion matches any position that is not ... Read More

Translation is similar, but not identical, to the principles of substitution in Perl, but unlike substitution, translation (or transliteration) does not use regular expressions for its search on replacement values. The translation operators are −tr/SEARCHLIST/REPLACEMENTLIST/cds y/SEARCHLIST/REPLACEMENTLIST/cdsThe translation replaces all occurrences of the characters in SEARCHLIST with the corresponding characters in ... Read More

The substitution operator s/// in Perl is really just an extension of the match operator that allows you to replace the text matched with some new text. The basic form of the operator is −s/PATTERN/REPLACEMENT/;The PATTERN is the regular expression for the text that we are looking for. The REPLACEMENT ... Read More

There is a simpler version of the match operator in Perl - the ?PATTERN? operator. This is basically identical to the m// operator except that it only matches once within the string you are searching between each call to reset.For example, you can use this to get the first and ... Read More

The match operator m// in Perl, is used to match a string or statement to a regular expression. For example, to match the character sequence "foo" against the scalar $bar, you might use a statement like this −Example Live Demo#!/usr/bin/perl $bar = "This is foo and again foo"; if ($bar =~ ... Read More

There are various File Handle related Special Variables in Perl. We have listed them in different below in tabular form:$|If set to nonzero, forces an fflush(3) after every write or print on the currently selected output channel.$OUTPUT_AUTOFLUSH$%The current page number of the currently selected output channel.$FORMAT_PAGE_NUMBER$=The current page length (printable ... Read More

There are various Regular Expression Special Variables in Perl. We have listed them in different below in tabular form −$digitContains the text matched by the corresponding set of parentheses in the last pattern matched. For example, $1 matches whatever was contained in the first set of parentheses in the previous ... Read More

There are various global special variables in Perl. We have listed them in different blocks based on their usage and nature −Global Array Special Variables@ARGVThe array containing the command-line arguments intended for the script.@INCThe array containing the list of places to look for Perl scripts to be evaluated by the ... Read More

The confess function in Perl is like cluck; it calls die and then prints a stack trace all the way up to the origination script.package T; require Exporter; @ISA = qw/Exporter/; @EXPORT = qw/function/; use Carp; sub function {    confess "Error in module!"; } 1;When called from a script ... Read More