You don't need to mess with typeglobs to do the second.

open(STDOUT, '> myfilename.txt'); #reopen STDOUT as a file
print "This goes to the file\n";
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Or

open(OUTFILE, '> myfilename.txt');
print "This goes to the screen\n";
open(STDOUT, '>&OUTFILE'); #dup STDOUT to OUTFILE
print "This goes to the file\n";
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