to create a working relative link, I need to do a chdir first

That would be the easiest way. However, it seems that you simply need to calculate the relative link (relative to the folder/directory where the symlink-to-be shall reside), e.g. with Path::Tiny->relative()

my $newname="/home/script/data/archive/currentfile";
my $targetfile="/home/script/data/archive/infofile-2019-12-16";

# untested
use Path::Tiny 'path';
my $newdir = path($newfile)->parent();
my $linktarget = path($targetfile)->relative($newdir);
print ":$linktarget:\n";
symlink $linktarget, $newname;
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