$ cat Foo.pm
use warnings;
CHECK { print "in check\n" }
INIT { print "in init\n" }
1;
$ perl -e'require Foo'
Too late to run CHECK block at Foo.pm line 2.
Too late to run INIT block at Foo.pm line 3.
$ perl -e'use diagnostics; require Foo'
Too late to run CHECK block at Foo.pm line 2 (#1)
    (W void) A CHECK or INIT block is being defined during run time proper,
    when the opportunity to run them has already passed.  Perhaps you are
    loading a file with require or do when you should be using use
    instead.  Or perhaps you should put the require or do inside a
    BEGIN block.
    
Too late to run INIT block at Foo.pm line 3 (#1)