diff options
Diffstat (limited to 'pod/perlfunc.pod')
| -rw-r--r-- | pod/perlfunc.pod | 43 |
1 files changed, 25 insertions, 18 deletions
diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod index 0761412f4a..2c198c1d45 100644 --- a/pod/perlfunc.pod +++ b/pod/perlfunc.pod @@ -3755,19 +3755,23 @@ rename(2) manpage or equivalent system documentation for details. =item require -Demands some semantics specified by EXPR, or by C<$_> if EXPR is not -supplied. +Demands a version of Perl specified by VERSION, or demands some semantics +specified by EXPR or by C<$_> if EXPR is not supplied. -If a VERSION is specified as a literal of the form v5.6.1, -demands that the current version of Perl (C<$^V> or $PERL_VERSION) be -at least as recent as that version, at run time. (For compatibility -with older versions of Perl, a numeric argument will also be interpreted -as VERSION.) Compare with L</use>, which can do a similar check at -compile time. +VERSION may be either a numeric argument such as 5.006, which will be +compared to C<$]>, or a literal of the form v5.6.1, which will be compared +to C<$^V> (aka $PERL_VERSION). A fatal error is produced at run time if +VERSION is greater than the version of the current Perl interpreter. +Compare with L</use>, which can do a similar check at compile time. + +Specifying VERSION as a literal of the form v5.6.1 should generally be +avoided, because it leads to misleading error messages under earlier +versions of Perl which do not support this syntax. The equivalent numeric +version should be used instead. require v5.6.1; # run time version check require 5.6.1; # ditto - require 5.005_03; # float version allowed for compatibility + require 5.006_001; # ditto; preferred for backwards compatibility Otherwise, demands that a library file be included if it hasn't already been included. The file is included via the do-FILE mechanism, which is @@ -5640,18 +5644,21 @@ package. It is exactly equivalent to except that Module I<must> be a bareword. -VERSION, which can be specified as a literal of the form v5.6.1, demands -that the current version of Perl (C<$^V> or $PERL_VERSION) be at least -as recent as that version. (For compatibility with older versions of Perl, -a numeric literal will also be interpreted as VERSION.) If the version -of the running Perl interpreter is less than VERSION, then an error -message is printed and Perl exits immediately without attempting to -parse the rest of the file. Compare with L</require>, which can do a -similar check at run time. +VERSION may be either a numeric argument such as 5.006, which will be +compared to C<$]>, or a literal of the form v5.6.1, which will be compared +to C<$^V> (aka $PERL_VERSION. A fatal error is produced if VERSION is +greater than the version of the current Perl interpreter; Perl will not +attempt to parse the rest of the file. Compare with L</require>, which can +do a similar check at run time. + +Specifying VERSION as a literal of the form v5.6.1 should generally be +avoided, because it leads to misleading error messages under earlier +versions of Perl which do not support this syntax. The equivalent numeric +version should be used instead. use v5.6.1; # compile time version check use 5.6.1; # ditto - use 5.005_03; # float version allowed for compatibility + use 5.006_001; # ditto; preferred for backwards compatibility This is often useful if you need to check the current Perl version before C<use>ing library modules that have changed in incompatible ways from |