I want to delete the consecutive duplicate lines. i.e. for example test.txt car speed

Question

Asked: June 11, 20262026-06-11T12:09:04+00:00 2026-06-11T12:09:04+00:00

I want to delete the consecutive duplicate lines. i.e. for example

**test.txt**
car
speed is good
bike 
slower than car
plane
super fast
super fast
bullet train 
super fast

This removes all the duplicate lines except the 1st occurance.

perl -ne 'print unless $a{$_}++'

But i want the ouput to be

    **test.txt**
    car
    speed is good
    bike 
    slower than car
    plane
    super fast
    bullet train 
    super fast

I tried this oneliner but this doesnt do anything but just prints the input.

perl -00 -F'<\w+>|</\w+>' -i.bak -lane 'foreach(@F){if ($_=~/\w+/ && ($a ne $_)){print "$_";$a=$_;}}'

How to do this???

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Editorial Team · Answer 1 · 2026-06-11T12:09:05+00:00

Editorial Team

Try:

perl -ne 'print unless (defined($prev) && ($_ eq $prev)); $prev=$_'

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