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Diffstat (limited to 'pod/perlmod.pod')
-rw-r--r-- | pod/perlmod.pod | 32 |
1 files changed, 31 insertions, 1 deletions
diff --git a/pod/perlmod.pod b/pod/perlmod.pod index c03862d64d..c80836c752 100644 --- a/pod/perlmod.pod +++ b/pod/perlmod.pod @@ -257,7 +257,8 @@ This also has implications for the use of the SUPER:: qualifier Four special subroutines act as package constructors and destructors. These are the C<BEGIN>, C<CHECK>, C<INIT>, and C<END> routines. The -C<sub> is optional for these routines. +C<sub> is optional for these routines. See the B<begincheck> program, at +the end of this section, to see them in action. A C<BEGIN> subroutine is executed as soon as possible, that is, the moment it is completely defined, even before the rest of the containing file @@ -301,6 +302,35 @@ Both C<BEGIN> and C<CHECK> blocks are run when you use the B<-c> switch for a compile-only syntax check, although your main code is not. +The B<begincheck> program makes it all clear, eventually: + + #!/usr/bin/perl + + # begincheck + + print " 8. Ordinary code runs at runtime.\n"; + + END { print "14. So this is the end of the tale.\n" } + INIT { print " 5. INIT blocks run FIFO just before runtime.\n" } + CHECK { print " 4. So this is the fourth line.\n" } + + print " 9. It runs in order, of course.\n"; + + BEGIN { print " 1. BEGIN blocks run FIFO during compilation.\n" } + END { print "13. Read perlmod for the rest of the story.\n" } + CHECK { print " 3. CHECK blocks run LIFO at compilation's end.\n" } + INIT { print " 6. Run this again, using Perl's -c switch.\n" } + + print "10. This is anti-obfuscated code.\n"; + + END { print "12. END blocks run LIFO at quitting time.\n" } + BEGIN { print " 2. So this line comes out second.\n" } + INIT { print " 7. You'll see the difference right away.\n" } + + print "11. It merely _looks_ like it should be confusing.\n"; + + __END__ + =head2 Perl Classes There is no special class syntax in Perl, but a package may act |