Question

The My_Module-module (used in this package) uses Signals::XSIG and sets $XSIG{'WINCH'}[1] = sub { ... };

use warnings;
use 5.014;
package Auto_sid;
use Exporter 'import';
our @EXPORT = qw(something);

use My_Module;

no warnings qw(redefine);

sub My_Module::list_to_big {
    my ( @arguments ) = @_;
    require Signals::XSIG;
    Signals::XSIG->import(%Signals::XSIG::XSIG);
    @{$Signals::XSIG::XSIG{'WINCH'}} = ();
    no Signals::XSIG;
    # ...
    # do something that My_Module normaly doesn't do and
    # which doesn't work when modified $SIG{'WINCH'}
    # ...
}

When I use this I get a lot of error-messages like:

"NUM63" is not exported by the Signals::XSIG module
"ARRAY(0xc23180)" is not exported by the Signals::XSIG module
"TRAP" is not exported by the Signals::XSIG module
"ARRAY(0xc119c8)" is not exported by the Signals::XSIG module
...

When I use use instead of require it works fine.
Why does this not work with require?

Answer 1

Because when you do this:

Signals::XSIG->import(%Signals::XSIG::XSIG);

you’re passing the contents of that hash to the import routine. As NUM63 and TRAP are signal names, and they are not valid exports for Signals::XSIG, you’re getting those errors.

You need to do this:

Signals::XSIG->import('%XSIG');

Because it recognizes Exporter recognizes the string '%XSIG' as one of the things it does export.