#!/usr/bin/perl
use strict;
use warnings;

my @AoA = (
    ['firstRowCol1 asdf87534', 'firstRowCol2 junk lj6t90'],
    ['secondRowCol1 mnhibvygt7','secondRowCol2 7d7d5434']
);

my(@kmers);
for my $x (@AoA)
{
    for my $y (@$x)
    {
        push @kmers, $y =~ /^(\w+)/; #first word of each element 
        print "@kmers\n";
    }
}

__END__
In the above code,

print @kmers."\n"; #prints...
1
2
3
4

print @kmers,"\n";  #prints...
firstRowCol1
firstRowCol1firstRowCol2
firstRowCol1firstRowCol2secondRowCol1
firstRowCol1firstRowCol2secondRowCol1secondRowCol2

print "@kmers\n";  #prints...
firstRowCol1
firstRowCol1 firstRowCol2
firstRowCol1 firstRowCol2 secondRowCol1
firstRowCol1 firstRowCol2 secondRowCol1 secondRowCol2