Ubuntu Unleashed 2013 Edition: Covering 12.10 and 13.04, Eighth Edition

Special Variables

Perl has a variety of special variables, which usually look like punctuation—$_, $!, and $]—and are all extremely useful for shorthand code. $_ is the default variable, $! is the error message returned by the operating system, and $] is the Perl version number.

$_ is perhaps the most useful of these. You will see that variable used often in this chapter. $_ is the Perl default variable, which is used when no argument is specified. For example, the following two statements are equivalent:

chomp;chomp($_);

The following loops are equivalent:

for $cow (@cattle) {        print "$cow says moo.\n";}for (@cattle)        {        print "$_ says moo.\n";}

For a complete listing of the special variables, see the perlvar man page.