I happen to need the flip-flop after reading Flipin good, or a total flop?. The following behavior puzzles me, why does the first version print "after"? Thanks. 
my @data = <DATA>;
print "Using lexical varible:\n";
foreach my $line (@data){
    if($line =~ /begin/../end/){
        print $line;
    }
}

print "\nNot using lexical varible:\n";
foreach (@data){
    if(/begin/../end/){
        print;
    }
}


__DATA__
before
begin
1
2
3
end
after

__RESULT__
Using lexical varible:
begin
1
2
3
end
after

Not using lexical varible:
begin
1
2
3
end

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In reply to why doesn't this flip-flop work? by johnnywang

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