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author | Michael G. Schwern <schwern@pobox.com> | 2003-05-13 11:33:05 -0700 |
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committer | Rafael Garcia-Suarez <rgarciasuarez@gmail.com> | 2003-07-11 18:54:09 +0000 |
commit | 6014d0cb2904bf89033c6aa0d3dbb1d1600d6994 (patch) | |
tree | 506b2b283a48cddee7fa8dc08ef97f0f3039b063 /pod/perlsyn.pod | |
parent | 103dd89994b01bc194bfaf186624c2fb15f80afe (diff) | |
download | perl-6014d0cb2904bf89033c6aa0d3dbb1d1600d6994.tar.gz |
New introduction
Message-ID: <20030514013305.GB22001@windhund.schwern.org>
p4raw-id: //depot/perl@20154
Diffstat (limited to 'pod/perlsyn.pod')
-rw-r--r-- | pod/perlsyn.pod | 44 |
1 files changed, 27 insertions, 17 deletions
diff --git a/pod/perlsyn.pod b/pod/perlsyn.pod index 5ddd7e1d45..9aec074dd1 100644 --- a/pod/perlsyn.pod +++ b/pod/perlsyn.pod @@ -4,23 +4,27 @@ perlsyn - Perl syntax =head1 DESCRIPTION -A Perl script consists of a sequence of declarations and statements. -The sequence of statements is executed just once, unlike in B<sed> -and B<awk> scripts, where the sequence of statements is executed -for each input line. While this means that you must explicitly -loop over the lines of your input file (or files), it also means -you have much more control over which files and which lines you look at. -(Actually, I'm lying--it is possible to do an implicit loop with -either the B<-n> or B<-p> switch. It's just not the mandatory -default like it is in B<sed> and B<awk>.) - -Perl is, for the most part, a free-form language. (The only exception -to this is format declarations, for obvious reasons.) Text from a -C<"#"> character until the end of the line is a comment, and is -ignored. If you attempt to use C</* */> C-style comments, it will be -interpreted either as division or pattern matching, depending on the -context, and C++ C<//> comments just look like a null regular -expression or defined-or operator, so don't do that. +A Perl program consists of a sequence of declarations and statements +which run from the top to the bottom. Loops, subroutines and other +control structures allow you to jump around within the code. + +Perl is a B<free-form> language, you can format and indent it however +you like. Whitespace mostly serves to separate tokens, unlike +languages like Python where it is an important part of the syntax. + +Many of Perl's syntactic elements are B<optional>. Rather than +requiring you to put parenthesis around every function call and +declare every variable, you can often leave such explicit elements off +and Perl will figure out what you meant. This is known as B<Do What I +Mean>, abbreviated B<DWIM>. It allows programmers to be B<lazy> and to +code in a style which they are comfortable. + +Perl B<borrows syntax> and concepts from many languages: awk, sed, C, +Bourne Shell, Smalltalk, Lisp and even English. Other +languages have borrowed syntax from Perl, particularly its regular +expression extensions. So if you have programmed in another language +you will see familiar pieces in Perl. They often work the same, but +see L<perltrap> for information about how they differ. =head2 Declarations @@ -79,6 +83,12 @@ like an ordinary statement, and is elaborated within the sequence of statements as if it were an ordinary statement. That means it actually has both compile-time and run-time effects. +=head2 Comments + +Text from a C<"#"> character until the end of the line is a comment, +and is ignored. Exceptions include C<"#"> inside a string or regular +expression. + =head2 Simple Statements The only kind of simple statement is an expression evaluated for its |