#!/usr/bin/perl

#  2024-0111: From the node: "Eliminate consecutive duplicates of list
#  elements. If a list contains repeated elements they should be
#  replaced with a single copy of the element. The order of the
#  elements should not be changed."

use strict;
use warnings;

{
    my @orig = qw/a a a a b c c a a d e e e e/;
    my @correct = qw/a b c a d e/;

    my @soln;
    for ( push ( @soln, shift @orig ); @orig; ) {

      my $val = shift @orig;
      if ( $soln[-1] ne $val ) { push ( @soln, $val ); }
    }

    print "Correct solution is @correct;\n";
    print "My solution is @soln.\n";
}
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Because my background (before Perl) is in C, that automatically looks like a for loop problem to me. In other words, you need to prime the pump so that you're not forced into doing something Really Clever for the first element.

And I could have written

    push ( @soln, $val ) if ( $soln[-1] ne $val );
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to make it more Perl-ish, but I'm not a fan of the postfix syntax. My OldSchool brain wants to see an if statement at the beginning of the line.

And, yes, this assumes that the list is string values (or stringable values), and does not deal with the undef value. That reminds me of a Google interview that I had a while back ("What about this ridiculous limitation to the solution?" "And how about this even more insane exception?").