[Perl-beginners] Re: Deleting Duplicate Lines one-liner

	Jeff 'japhy/Marillion' Pinyan
	Jul 30, 2001 at 6:47 pm

On Jul 30, Paul said:

--- Jeff 'japhy/Marillion' Pinyan wrote:

perl -pe '$_ x= !$seen{$_}++' (attributed to some of Larry's genius)

LOL!!! Twistedly brilliant!

Ok, lemme see if I can parse this.....
[correct prognosis snipped]
Is that right?

Yes. I attribute that to Larry Wall, because he wrote something like

perl -pe '$_ x= /pattern/'

to make a poor man's grep. I found that beautiful.

--
Jeff "japhy" Pinyan japhy@pobox.com http://www.pobox.com/~japhy/
RPI Acacia brother #734 http://www.perlmonks.org/ http://www.cpan.org/
** Look for "Regular Expressions in Perl" published by Manning, in 2002 **

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Paul: LOL!!! Twistedly brilliant! Ok, lemme see if I can parse this..... perl -pe says print each line after the -e code has been executed. "$_ x= !$seen{$_}++" says: $_ x= assign to $_ itself, repeated a number of times !$seen{$_} evaluate $seen{$_} in a negated boolean context for the number postfix ++ increments after returning the previous value. so "$_ x= !$seen{$_}++" says 1) check $seen{$_} (have we seen this before) 2) then increment it (we've seen it now!) 3) negate the boolean value of

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