/.*?\n/ isn't really any slower, since it jumps to the closest newline it finds. The silly thing is the ? in that regex. The .*? in your regex WON'T match over the newlines, so you're missing an /s modifier I think. And since [^\n] IS ., I'd just write: 
{
  local $/;
  my ($num, $from) = <FILE> =~ m{
    mailbox \s+ (\d+): \s+
    From: \s* (.*)
  }x;
}

[download]
Untested, but it seems to me that it should work properly, given the data from the OP.
Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

In reply to Re^2: A little regex help please! by japhy
in thread A little regex help please! by jdtoronto

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