It's a matter of operator precedence1: 
$ perl -e 'm/foo/i && print while <>'
i was foo
i was foo
i was fee
i was foolish
i was foolish
^D
$

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[1] Update: And, as MeowChow says, a single modifier.

After Compline,
Zaxo

In reply to Re: Perl and the magic of the perl compiler by Zaxo
in thread Perl and the magic of the perl compiler by coolmichael

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