X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperltrap.pod;h=c59ecc4dafabcf8beec1411a787c1ce9f7026717;hb=6940069f6d5beebb5f66572e358b4e7d0c3d1c43;hp=852d8e98263e686c0ecc116c0d12fd151edd52cb;hpb=c12982c86a2196a797f6a6b78ff87ba73a7de7fe;p=p5sagit%2Fp5-mst-13.2.git diff --git a/pod/perltrap.pod b/pod/perltrap.pod index 852d8e9..c59ecc4 100644 --- a/pod/perltrap.pod +++ b/pod/perltrap.pod @@ -22,7 +22,7 @@ The English module, loaded via use English; allows you to refer to special variables (like C<$/>) with names (like -C<$RS>), as though they were in B; see L for details. +$RS), as though they were in B; see L for details. =item * @@ -69,7 +69,7 @@ executed.) See L. =item * -$EIE does not refer to fields--it refers to substrings matched +$> does not refer to fields--it refers to substrings matched by the last match pattern. =item * @@ -103,7 +103,7 @@ basically incompatible with C.) The concatenation operator is ".", not the null string. (Using the null string would render C unparsable, because the third slash would be interpreted as a division operator--the tokenizer is in fact -slightly context sensitive for operators like "/", "?", and "E". +slightly context sensitive for operators like "/", "?", and ">". And in fact, "." itself can be the beginning of a number.) =item * @@ -160,7 +160,7 @@ You must use C rather than C. The C and C keywords from C become in Perl C and C, respectively. -Unlike in C, these do I work within a C construct. +Unlike in C, these do I work within a C construct. =item * @@ -172,12 +172,6 @@ Variables begin with "$", "@" or "%" in Perl. =item * -C does not implement the "*" format for interpolating -field widths, but it's trivial to use interpolation of double-quoted -strings to achieve the same effect. - -=item * - Comments begin with "#", not "/*". =item * @@ -295,7 +289,7 @@ you might expect to do not. =item * -The EFHE construct is not the name of the filehandle, it is a readline +The construct is not the name of the filehandle, it is a readline operation on that handle. The data read is assigned to $_ only if the file read is the sole condition in a while loop: @@ -305,7 +299,7 @@ file read is the sole condition in a while loop: =item * -Remember not to use "C<=>" when you need "C<=~>"; +Remember not to use C<=> when you need C<=~>; these two constructs are quite different: $x = /foo/; @@ -392,8 +386,9 @@ Everything else. =back If you find an example of a conversion trap that is not listed here, -please submit it to Bill Middleton > for inclusion. -Also note that at least some of these can be caught with B<-w>. +please submit it to > for inclusion. +Also note that at least some of these can be caught with the +C pragma or the B<-w> switch. =head2 Discontinuance, Deprecation, and BugFix traps @@ -424,7 +419,7 @@ behave differently in perl4 vs. perl5, because the packages don't exist. $a=1;$b=2;$c=3;$var=4; print "$a::$b::$c "; print "$var::abc::xyz\n"; - + # perl4 prints: 1::2::3 4::abc::xyz # perl5 prints: 3 @@ -585,30 +580,18 @@ number of elements in the resulting list. # perl4 prints: second new # perl5 prints: 3 -=item * Discontinuance - -In Perl 4 (and versions of Perl 5 before 5.004), C<'\r'> characters in -Perl code were silently allowed, although they could cause (mysterious!) -failures in certain constructs, particularly here documents. Now, -C<'\r'> characters cause an immediate fatal error. (Note: In this -example, the notation B<\015> represents the incorrect line -ending. Depending upon your text viewer, it will look different.) - - print "foo";\015 - print "bar"; - - # perl4 prints: foobar - # perl5.003 prints: foobar - # perl5.004 dies: Illegal character \015 (carriage return) - -See L for full details. - =item * Deprecation Some error messages will be different. =item * Discontinuance +In Perl 4, if in list context the delimiters to the first argument of +C were C, the result would be placed in C<@_> as well as +being returned. Perl 5 has more respect for your subroutine arguments. + +=item * Discontinuance + Some bugs may have been inadvertently removed. :-) =back @@ -715,6 +698,30 @@ Logical tests now return an null, instead of 0 Also see L<"General Regular Expression Traps using s///, etc."> for another example of this new feature... +=item * Bitwise string ops + +When bitwise operators which can operate upon either numbers or +strings (C<& | ^ ~>) are given only strings as arguments, perl4 would +treat the operands as bitstrings so long as the program contained a call +to the C function. perl5 treats the string operands as bitstrings. +(See L for more details.) + + $fred = "10"; + $barney = "12"; + $betty = $fred & $barney; + print "$betty\n"; + # Uncomment the next line to change perl4's behavior + # ($dummy) = vec("dummy", 0, 0); + + # Perl4 prints: + 8 + + # Perl5 prints: + 10 + + # If vec() is used anywhere in the program, both print: + 10 + =back =head2 General data type traps @@ -761,6 +768,9 @@ Hashes get defined before use # perl4 prints: # perl5 dies: hash %h defined +Perl will now generate a warning when it sees defined(@a) and +defined(%h). + =item * (Globs) glob assignment from variable to variable will fail if the assigned @@ -1056,7 +1066,7 @@ All types of RE traps. =item * Regular Expression C now does no interpolation on either side. It used to -interpolate C<$lhs> but not C<$rhs>. (And still does not match a literal +interpolate $lhs but not $rhs. (And still does not match a literal '$' in string) $a=1;$b=2; @@ -1095,7 +1105,7 @@ the very first time in any such closure. For instance, if you say } build_match() will always return a sub which matches the contents of -C<$left> and C<$right> as they were the I time that build_match() +$left and $right as they were the I time that build_match() was called, not as they are in the current call. This is probably a bug, and may change in future versions of Perl. @@ -1257,7 +1267,7 @@ Since version 5.002, Perl uses sigaction() under SysV. =item * (SysV) -Under SysV OSes, C on a file opened to append CE> now does +Under SysV OSes, C on a file opened to append C<<< >> >>> now does the right thing w.r.t. the fopen() manpage. e.g., - When a file is opened for append, it is impossible to overwrite information already in the file. @@ -1292,7 +1302,8 @@ within certain expressions, statements, contexts, or whatever. print "To: someone@somewhere.com\n"; # perl4 prints: To:someone@somewhere.com - # perl5 errors : In string, @somewhere now must be written as \@somewhere + # perl < 5.6.1, error : In string, @somewhere now must be written as \@somewhere + # perl >= 5.6.1, warning : Possible unintended interpolation of @somewhere in string =item * Interpolation @@ -1327,7 +1338,7 @@ Note that you can C to ward off such trappiness under perl5. =item * Interpolation The construct "this is $$x" used to interpolate the pid at that -point, but now apparently tries to dereference C<$x>. C<$$> by itself still +point, but now apparently tries to dereference $x. C<$$> by itself still works fine, however. print "this is $$x\n";