Note: I remember I once used a single assignment to basically do the same with what for does above, but I can't find references about that in the official docs anymore. The assignment below,

*main:: = *my_temp_convert::;
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gives me a "Modification of a read-only value" fatal exception. I'm not sure if that's the correct syntax I used or thing has changed. Any monk knows what happens?

What happens is just what you noticed. The symbol table typeglob itself is read-only. Assigning the symbol table hash itself doesn't help either (because it clobbers the table):

package foo;
sub foo {print "bar"};
package main;
%main:: = %foo::;
print "$_ => $main::{$_}" for keys %main::;
foo();
__END__
foo => *foo::foo
Undefined subroutine &main::foo called at -e line 1.
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so the shortest way to do the assignment you want is using a "hash slice":

@main::{ keys %foo:: } = values %foo::;
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