I've been trapped by this regexp behaviour before, and I got trapped again.

The problem this time:
I have a file with tab separated data.
The data is intended for loading into a mysql databas.
Because of that I shall replace every empty field with a null mark (in this case \N).
So every tab that is immediatly followed by another tab or newline (or end of file) should have this "\N" attached to it.

Walking right into the trap 

$line =~ s/\t([\t\n])/\t\\N$1/g;

[download]
And of course, when two empty fields are following one eachother my regexp fails doing what I want.
This little snippet (where I am using pipes as separators, for the sake of visibility) illustrates my point. 
while (my $line = <DATA>) {
    $line =~ s/\|(\||$)/\|\\N$1/g;
    print $line;
}
__DATA__
a|||d|

[download]
The output will be:
a|\N||d|\N

How do you guys usually deal with this? If someone can come up with an one-liner it would really suit me best.
Thanks in advance
/L

In reply to Regexp: Overlapping matches by Anonymous Monk

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