#!/usr/bin/perl

use strict;
use Data::Dumper;

my $line = q[keyword1 value keyword2 "value with spaces" keyword3 value];

print Dumper tokenize_line($line);

sub tokenize_line {
    my $line = shift;

    my @tokens;
    while ($line =~ /(\S+)/g) {
        # every non-space match is a token
        push @tokens, $1;

        # anything in double-quotes is a single token
        if ($line =~ /\G\s*"(.+?)"/) {
            push @tokens, $1;
            # continue from this last match
            $line = $';
        }
    }

    return \@tokens;
}