Thanks. But is this the best way to do syntax check of a module ?

What metric should I use to judge whether it's the best besides "It works"?

This is happening because base ends up requireing Foo, which in turns ends up doing Foo.pm, since it hasn't been donerequired yet ...

Update 2: The safeguard is in require, of course. ikegami++. The workaround below is still useful for those "executable modules", but unnecessary for most purposes.

(Oh, and for completeness, use happens at compile time, and so is run even with the -c option.)

Update: A workaround: Add a $VERSION variable to Foo, as this prevents base from trying to load it again:

package Foo;

our $VERSION = 0.001;

sub test { }

1;

package Bar;
use base Foo;

sub test2 { }

1;
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base does a require of the module in question itself, so basically you're pulling in the same file in the middle of parsing itself. Either move Bar to its own file, or eschew base and just set @ISA yourself.

Update: Nevermind me, ikegami's got it.

$ perl -c -we '1'
-e syntax OK
$ perl -c -we '3'
Useless use of a constant in void context at -e line 1.
-e syntax OK
$ perl -c -we '"OK"'
Useless use of a constant in void context at -e line 1.
-e syntax OK
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This warning will not be issued for numerical constants equal to 0 or 1 since they are often used in statements like

   1 while sub_with_side_effects();
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String constants that would normally evaluate to 0 or 1 are warned about.