sub print_darwin {
    my $main = shift;
    my $ps_filename = shift;
    my $ret = system( 'open', '-a', 'Preview', $ps_filename );
    if ( $ret == -1 ) {
        die "could not execute 'open -a Preview $ps_filename': $!";
    }
    elsif ($ret)      {
        die " failed in 'open -a Preview $ps_filename': $?";
    }
    return;
}
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