In Perl 5 you need parenthesis directly after the 'if',

Except if you use the if statement modifier 

bar() if foo();

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Mind you, the statement modifier wouldn't be useful here. The condition operator, on the other hand, would be useful. 

$user_input->{end_date} = defined(param('end_date'))
    ? param('end_date')
    : param('start_date');

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Mind you, param('end_date') can still be called twice for nothing. The following doesn't: 

$user_input->{end_date} = param('end_date');
$user_input->{end_date} = param('start_date')
    if !defined($user_input->{end_date});

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Since 5.10, the above can be simplified to the following: 
$user_input->{end_date} = param('end_date') // param('start_date');

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The following isn't strictly equivalent, but should do the trick if you want something similar while still supporting earlier versions of Perl: 
$user_input->{end_date} = param('end_date') || param('start_date');

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In reply to Re^2: syntax of defined by ikegami
in thread syntax of defined by siddheshsawant

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