Perl has two for loops:

  1. C-style: for (...; ...; ...) { ... }

  2. List-style (foreach): for (LIST) { ... }

Only the second (“foreach”) is available as a statement modifier:

EXPRESSION for LIST;

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So in the second example, the code is effectively:

printf "_=%s\n", $_ for $_ = 3;
$_-- > 0;

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The first line prints _=3, the second line decrements $_ but has no other effect.

Update: Even for one-liners, you should turn on warnings:

perl -wE ...

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This often gives an insight into what Perl understands your code to be. For example:

13:44 >perl -wE "printf qq[_=%s], $_ for $_ = 3; $_-- > 0;"
Useless use of numeric gt (>) in void context at -e line 1.
_=3
13:45 >

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Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

In reply to Re: Why/how are these different? by Athanasius
in thread Why/how are these different? by perl-diddler

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