package execOverride;     # execOverride.pm

*CORE::GLOBAL::exec = sub {
   my $cmd = shift;
   print "Called exec override\n";
   CORE::exec($cmd);
};
1;


# main script
#!/usr/bin/perl
    
use execOverride;

exec("/bin/echo foo");

__END__
$ ./830161.pl
Called exec override
foo