You can reset STDOUT in BEGIN block, Please refere follwoing code snippet, it might be helpful you.

BEGIN {
    open STDERR, '> log.txt'
        or die "Can't Write to log.txt. Permission Denied!!!";
    binmode STDERR;
}
&pager();

sub pager { 
        my $temp = "temp.txt";
        my $pager = "less"; 
        system("$pager $temp");
}
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