What is the post-for/if syntax called?

Does the following syntax have a name?

print for ( @ARG开发者_如何学JAVAV );

exit if $x;

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They're statement modifiers.

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It's called "Statement Modifiers" in the perlsyn documentation.

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Sometimes they are known as postfix constructions.

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If you mean the the components of the snippet, yes, those are statement modifiers.

If you mean the construct of the statement I would say following:

pre-condition/prefix construct:

... the condition (if $x) is written before (pre) the statement ( { ... exit ...;})

It's the normal (most used) way to write those statements.

for ( @ARGV ){
    print;
}

if ($x) {
    exit;
}

post-condition/postfix construct:

... the condition (if $x) is written after (post) the statement ( { ... exit ...;})

It's the other way around. Mostly for shortcuts, or one-liners. Some find it usefull, but it's generally discouraged because or readability and understanding: see @mob's answer
Or from PerlMonks: https://www.perlmonks.org/?node_id=177971

print for ( @ARGV );

exit if $x;