If you want an "else" with an if, you need the brackets, "if" after the statement is a modifier, not a control block... if you just need the else, use unless

print "OK\n" unless $a == 1;
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Update: I suppose you could do

print "OK\n"     if     $a == 1;
print "Not OK\n" unless $a == 1;
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But don't. ;)