Once again you're splicing the wrong array :) If you want to remove a row, then you want to alter the outer array, @R.

But in this case, splice is really the wrong tool. Here you probably want to use grep.

#!/usr/bin/perl

use strict;
use warnings;

use Data::Dumper;

my @R = ([qw(x y z)], [qw(a b c)], [qw(e f g)], [qw(h i j)]);

print Dumper \@R;

@R = grep { $_->[0] ne 'a' } @R;

print Dumper \@R;
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