=item *
The concatenation operator is ".", not the null string. (Using the
-null string would render C</pat/ /pat/> unparsable, since the third slash
-would be interpreted as a division operator--the tokener is in fact
+null string would render C</pat/ /pat/> unparsable, because the third slash
+would be interpreted as a division operator--the tokenizer is in fact
slightly context sensitive for operators like "/", "?", and "E<gt>".
And in fact, "." itself can be the beginning of a number.)
=item *
You can't take the address of anything, although a similar operator
-in Perl 5 is the backslash, which creates a reference.
+in Perl is the backslash, which creates a reference.
=item *
=item *
-The backtick operator does variable interpolation without regard to
+The back-tick operator does variable interpolation without regard to
the presence of single quotes in the command.
=item *
-The backtick operator does no translation of the return value, unlike B<csh>.
+The back-tick operator does no translation of the return value, unlike B<csh>.
=item *
Shells (especially B<csh>) do several levels of substitution on each
-command line. Perl does substitution only in certain constructs
-such as double quotes, backticks, angle brackets, and search patterns.
+command line. Perl does substitution in only certain constructs
+such as double quotes, back-ticks, angle brackets, and search patterns.
=item *
=item *
Avoid barewords if you can, especially all lower-case ones.
-You can't tell just by looking at it whether a bareword is
+You can't tell by just looking at it whether a bareword is
a function or a string. By using quotes on strings and
-parens on function calls, you won't ever get them confused.
+parentheses on function calls, you won't ever get them confused.
=item *
You cannot discern from mere inspection which built-ins
are unary operators (like chop() and chdir())
and which are list operators (like print() and unlink()).
-(User-defined subroutines can B<only> be list operators, never
+(User-defined subroutines can be B<only> list operators, never
unary ones.) See L<perlop>.
=item *
=item *
The E<lt>FHE<gt> construct is not the name of the filehandle, it is a readline
-operation on that handle. The data read is only assigned to $_ if the
+operation on that handle. The data read is assigned to $_ only if the
file read is the sole condition in a while loop:
while (<FH>) { }
=back
-=head2 Perl4 to Perl5 Traps
+=head2 Perl4 to Perl5 Traps
Practicing Perl4 Programmers should take note of the following
Perl4-to-Perl5 specific traps.
=item * Deprecation
Double-colon is now a valid package separator in a variable name. Thus these
-behave differently in perl4 vs. perl5, since the packages don't exist.
+behave differently in perl4 vs. perl5, because the packages don't exist.
$a=1;$b=2;$c=3;$var=4;
print "$a::$b::$c ";
=item * Numerical
-This specific item has been deleted. It demonstrated how the autoincrement
+This specific item has been deleted. It demonstrated how the auto-increment
operator would not catch when a number went over the signed int limit. Fixed
-in 5.003_04. But always be wary when using large ints. If in doubt:
+in 5.003_04. But always be wary when using large integers. If in doubt:
use Math::BigInt;
Variable suicide behavior is more consistent under Perl 5.
Perl5 exhibits the same behavior for associative arrays and scalars,
-that perl4 exhibits only for scalars.
+that perl4 exhibits for only scalars.
$aGlobal{ "aKey" } = "global value";
print "MAIN:", $aGlobal{"aKey"}, "\n";
open FOO || die;
-is now incorrect. You need parens around the filehandle.
-Otherwise, perl5 leaves the statement as it's default precedence:
+is now incorrect. You need parentheses around the filehandle.
+Otherwise, perl5 leaves the statement as its default precedence:
open(FOO || die);
=item * Regular Expression
-C<s`lhs`rhs`> (using backticks) is now a normal substitution, with no
-backtick expansion
+C<s`lhs`rhs`> (using back-ticks) is now a normal substitution, with no
+back-tick expansion
$string = "";
$string =~ s`^`hostname`;
=item * (SysV)
Under SysV OS's, C<seek()> on a file opened to append C<E<gt>E<gt>> now does
-the right thing w.r.t. the fopen() man page. e.g. - When a file is opened
+the right thing w.r.t. the fopen() man page. e.g., - When a file is opened
for append, it is impossible to overwrite information already in
the file.
projects / p5sagit/p5-mst-13.2.git / blobdiff