X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperlsyn.pod;h=28bb824ada99bf497848e2193ec0fb33941d9a6f;hb=6e0733998eff7a098d2d21d5602f3eb2a7521e1f;hp=177ff4c4b99810e930131784a8c73f62ebf905a9;hpb=8c02634dc0c7d7611687ee447f001fcf1c387de5;p=p5sagit%2Fp5-mst-13.2.git diff --git a/pod/perlsyn.pod b/pod/perlsyn.pod index 177ff4c..28bb824 100644 --- a/pod/perlsyn.pod +++ b/pod/perlsyn.pod @@ -117,7 +117,7 @@ is treated as 0. =head2 Statement Modifiers X X X X X -X X X +X X X X Any simple statement may optionally be followed by a I modifier, just before the terminating semicolon (or block ending). The possible @@ -127,6 +127,8 @@ modifiers are: unless EXPR while EXPR until EXPR + when EXPR + for LIST foreach LIST The C following the modifier is referred to as the "condition". @@ -139,6 +141,22 @@ the condition is true (i.e., if the condition is false). print "Basset hounds got long ears" if length $ear >= 10; go_outside() and play() unless $is_raining; +C executes the statement I C<$_> smart matches C, and +then either Cs out if it's enclosed in a C scope or skips +to the C element when it lies directly inside a C loop. +See also L. + + given ($something) { + $abc = 1 when /^abc/; + $just_a = 1 when /^a/; + $other = 1; + } + + for (@names) { + admin($_) when [ qw/Alice Bob/ ]; + regular($_) when [ qw/Chris David Ellen/ ]; + } + The C modifier is an iterator: it executes the statement once for each item in the LIST (with C<$_> aliased to each item in turn). @@ -560,25 +578,25 @@ time. The exceptions are that when EXPR is: =over 4 -=item o +=item * a subroutine or method call -=item o +=item * a regular expression match, i.e. C or C<$foo =~ /REGEX/>, or a negated regular expression match C<$foo !~ /REGEX/>. -=item o +=item * a comparison such as C<$_ E 10> or C<$x eq "abc"> (or of course C<$_ ~~ $c>) -=item o +=item * C, C, or C -=item o +=item * A negated expression C or C, or a logical exclusive-or C<(...) xor (...)>. @@ -607,7 +625,7 @@ is applied recursively to the first argument. These rules look complicated, but usually they will do what you want. For example you could write: - when (/^\d$/ && $_ < 75) { ... } + when (/^\d+$/ && $_ < 75) { ... } Another useful shortcut is that, if you use a literal array or hash as the argument to C, it is turned into a @@ -634,7 +652,7 @@ case to the next: given($foo) { when (/x/) { say '$foo contains an x'; continue } when (/y/) { say '$foo contains a y' } - default { say '$foo contains neither an x nor a y' } + default { say '$foo does not contain a y' } } =head3 Switching in a loop @@ -674,7 +692,7 @@ order, determines the match behaviour. Any Code[+] scalar sub truth $b->($a) Hash Hash hash keys identical [sort keys %$a]~~[sort keys %$b] - Hash Array hash value slice truth grep $_, @$a{@$b} + Hash Array hash slice existence @$b == grep {exists $a->{$_}} @$b Hash Regex hash key grep grep /$b/, keys %$a Hash Any hash entry existence exists $a->{$b} @@ -716,7 +734,8 @@ See L. The Perl 5 smart match and C/C constructs are not absolutely identical to their Perl 6 analogues. The most visible difference is that, in Perl 5, parentheses are required around -the argument to C and C. Parentheses in Perl 6 +the argument to C and C (except when this last +one is used as a statement modifier). Parentheses in Perl 6 are always optional in a control construct such as C, C, or C; they can't be made optional in Perl 5 without a great deal of potential confusion, because Perl 5