Why I can't use if(defined $var)?

[Peng Yu]

I'm puzzled why I can not use the first line below. Would you please
let me know how write it such that the if clause is at the beginning
rather than at the end.

if(defined $opt_o) print "$opt_o\n";

print "$opt_o\n" if defined $opt_o;

Regards,
Peng

 

[sisyphus]

I'm puzzled why I can not use the first line below. Would you please
let me know how write it such that the if clause is at the beginning
rather than at the end.

if(defined $opt_o) print "$opt_o\n";

if(defined $opt_o) { print "$opt_o\n" }

Cheers,
Rob

 

[Dr.Ruud]

Would you please
let me know how write it such that the if clause is at the beginning
rather than at the end.

if(defined $opt_o) print "$opt_o\n";

defined $opt_o and print $opt_o, $/;