use strict;
use warnings;
my $string = 'www.perlmonks.org.split.reduce.code.check';
my @array = reverse split /\./, $string;
print "Reversed data ==> @array\n";
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Hi madtoperl,

A oneliner you say?

$ echo abc.def.ghi.jkl.mno | \
  perl -lne 'print join ".", reverse split /\./'
mno.jkl.ghi.def.abc
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Update: Golfed a tiny bit. If your shell causes you trouble with the backslash, try -F"[.]" instead.

$ echo abc.def.ghi.jkl.mno | \
  perl -F'\.' -lpe'$_=join".",reverse@F'
mno.jkl.ghi.def.abc
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Documentation of the switches is in perlrun.

Regards,
-- Hauke D

Is it about efficiency or number of lines? In the first case, you'll have to Benchmark a bunch of solutions. Otherwise, TIMTOWTDI.

$string = 'www.perlmonks.org.split.reduce.code.check';
print join " ", reverse( $string  =~ /(\w+)/g);

$, = " ";
print reverse (split /[.]/, $string);

my $out;
$out = "$_ $out" for split /[.]/, $string; # Extra space at the end th
+ough
print $out;
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If efficiency is defined by keystrokes, you may save a few by using capturing parens in your split. You may also rely on the fact that the -n flag loads one line at a time into $_, and that split looks at $_ if no other string param is provided:

echo www.perlmonks.org.split.reduce.code.check |perl -lnE 'say reverse
+ split /(\.)/'
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So this is 36 keystrokes if you start counting after the pipe. Someone will probably beat it though. One way to beat it will be eliminating two unneeded whitespace characters, so this gets it down to 34:

echo www.perlmonks.org.split.reduce.code.check |perl -lnE'say reverse 
+split/(\.)/'
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If efficiency is defined by some other metric, you would probably need to benchmark a few alternatives according to that metric to determine which one wins.

Another way using pop rather than reverse.

johngg@shiraz:~/perl/Monks > perl -Mstrict -Mwarnings -E '
say join q{.}, sub { map { pop } 1 .. @_ }->
   ( split m{\.}, shift );' www.perlmonks.org.split.reduce.code.check
check.code.reduce.split.org.perlmonks.www
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Update: Golfing this a bit still can't match davido's solution.

echo www.perlmonks.org.split.reduce.code.check | perl -lnE 'say sub{ma
+p pop,@_}->(split/(\.)/)'
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The race is on....

This shaves two strokes off my previous version.

# -2 strokes:
echo www.perlmonks.org.split.reduce.code.check |perl -lF'(\.)' -E'say 
+reverse@F'
# Compare to:
echo www.perlmonks.org.split.reduce.code.check |perl -lnE'say reverse 
+split/(\.)/'
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-F'pattern' sets -a auto-split mode with the pattern specified. The auto-split goes into @F. The -F field also sets -n automatically. So the original version and this version work essentially the same way, just relying on different ways to specify the split.




Dave

On that basis the following should work but it doesn't ...

$ echo www.perlmonks.org.split.reduce.code.check | perl -lF'(\.)' -E's
+ay sub{map pop,@_}->(@F)'

$
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... and I can't think why at the moment. Perhaps I'm misunderstanding what you have done :-/

Cheers,

JohnGG