Have you considered using IO::Tee instead of launching tee as separate process?

#!/usr/bin/perl -w

use strict;

use IO::Tee;

open FH,">somefile" or die "error opening $!";
my $tee=IO::Tee->new(\*STDOUT,\*FH);
select $tee;
print "foo\n";
print "bar\n";

close FH;
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