You can always test something like that with a one-liner.

% perl -wle '1 unless 2 or (3 and 4) if (5 and 6)'
syntax error at -e line 1, near ") if"
Execution of -e aborted due to compilation errors.
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On the other hand, statement modifiers at the end are syntactically OK; e.g. 1 or 2 if 3.

Whether it is good programming is less clear-cut.

I like using statement modifiers rather than regular if-else blocks whenever the contents of the blocks would have been short. I.e.

bar() if $foo;
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rather than

if ( $foo ) {
  bar();
}
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And sometimes I stretch it to statements like

bar() or baz() if $foo;
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in preference over

if ( $foo ) {
  unless ( bar() ) {
    baz();
  }
}
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...but I suspect this is already inching into obfuscation.

Great question++, BTW. I look forward to reading the responses you get.