sub myname;
$me = myname $0 or die "can't get myname";
-Note that my() functions as a list operator, not as a unary operator; so
-be careful to use C<or> instead of C<||> in this case. However, if
+Note that myname() functions as a list operator, not as a unary operator;
+so be careful to use C<or> instead of C<||> in this case. However, if
you were to declare the subroutine as C<sub myname ($)>, then
C<myname> would function as a unary operator, so either C<or> or
C<||> would work.
refers to the innermost enclosing loop. This may include dynamically
looking back your call-stack at run time to find the LABEL. Such
desperate behavior triggers a warning if you use the C<use warnings>
-praga or the B<-w> flag.
+pragma or the B<-w> flag.
Unlike a C<foreach> statement, a C<while> statement never implicitly
localises any variables.
for (@ary) { s/foo/bar/ }
- foreach my $elem (@elements) {
+ for my $elem (@elements) {
$elem *= 2;
}
Whereas here's how a Perl programmer more comfortable with the idiom might
do it:
- OUTER: foreach my $wid (@ary1) {
- INNER: foreach my $jet (@ary2) {
+ OUTER: for my $wid (@ary1) {
+ INNER: for my $jet (@ary2) {
next OUTER if $wid > $jet;
$wid += $jet;
}
Or if you are certainly that all the C<&&> clauses are true, you can use
something like this, which "switches" on the value of the
-C<HTTP_USER_AGENT> envariable.
+C<HTTP_USER_AGENT> environment variable.
#!/usr/bin/perl
# pick out jargon file page based on browser
dynamically. This allows for computed C<goto>s per FORTRAN, but isn't
necessarily recommended if you're optimizing for maintainability:
- goto ("FOO", "BAR", "GLARCH")[$i];
+ goto(("FOO", "BAR", "GLARCH")[$i]);
The C<goto>-&NAME form is highly magical, and substitutes a call to the
named subroutine for the currently running subroutine. This is used by
number for the next line, and C<$2> being the optional filename
(specified within quotes).
+There is a fairly obvious gotcha included with the line directive:
+Debuggers and profilers will only show the last source line to appear
+at a particular line number in a given file. Care should be taken not
+to cause line number collisions in code you'd like to debug later.
+
Here are some examples that you should be able to type into your command
shell: