You can't rely on readline returning EOF or errors more than once. Fix: 

OUTER: {
   for (;;) {
      defined( my $_ = <$fh> ) or last OUTER;
      if (/alpha/) {
         f();
         last;
      } else {
         g();
      }
   }

   while (<$fh>) {
      g();
   }
}

[download]

Update: The remainder of this post is wrong.

You can get rid of the duplicate g() by making the loops bottom tested. 

OUTER: {
   defined( my $_ = <$fh> ) or last OUTER;

   for (;;) {
      if (/alpha/) {
         f();
         last;
      }

      defined( $_ = <$fh> ) or last OUTER;
   }

   for (;;) {
      g();

      defined( $_ = <$fh> ) or last OUTER;
   }
}

[download]

You can squish it down a bit: 

LOOP: {
   defined( my $_ = <$fh> ) or last;

   if (/alpha/) {
      f();
      redo;
   }

   for (;;) {
      g();
      defined( $_ = <$fh> ) or last;
   }
}

[download]

Look at that, g() is not even duplicated anymore!!

In reply to Re^2: A way to avoid repeated conditional loops by ikegami
in thread A way to avoid repeated conditional loops by Deus Ex

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