If it is okay to substitute the string you could do this:

    #!/usr/bin/perl -wl

    use strict;

    my $s = "FOO=1 BAR= RED BOO = 5.6 BAZ =3";

    my %h;
    $h{lc $1} = $2 while $s =~ s/(\S+)\s*=\s*(\S+)//;

    print $_, "\t=> ", $h{$_} for keys  %h;

    __END__
    Prints:

    foo     => 1
    baz     => 3
    bar     => RED
    boo     => 5.6
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Or you could do something like this:

    #!/usr/bin/perl -wl

    use strict;

    my $s =  "FOO=1 BAR= RED BOO = 5.6 BAZ =3";

    my @a = split /[\s=]+/, $s;
    my %h = map {$_%2 ? $a[$_] : lc $a[$_]} 0..$#a;

    print $_, "\t=> ", $h{$_} for keys  %h;
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--
John.

It is possible, but using a while loop is better:

my $raw = "foo=1 baR= red BOO = 5.6 Baz =3";
my %params = ();

use Benchmark qw/cmpthese/;

my $test = {
    'map' => sub {
        %params =
          map { (lc($_) => $raw =~ /$_\s*=\s*(\S+)/ ) }
          $raw =~ /(\S+)\s*=/g;
        %params = ();
    },
    'while' => sub {

        $params{lc($1)} = $2 while
              $raw =~ /(\S+)\s*=\s*(\S+)/g;
        %params = ();
    }
};

#no regexp initialisation in benchmark
$_->() for values %$test;

cmpthese( -4 , $test );
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my $count;
my %params = map { ++$count % 2 ? lc : $_ } $raw =~ /(\S+)\s*=\s*(\S+)
+/g;
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my %params = map { ++$. % 2 ? lc : $_ } $raw =~ /(\S+)\s*=\s*(\S+)/g;
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~Particle *accelerates*

/e can be your friend. Try this:   $raw =~ s/(\S+?)\s*=\s*(\S+)/$params{lc($1)} = $2/ge; It's destructive on $raw, but that's easy enough to work around if you care.

I'm not great with regexes but couldnt you do something like:

my %params = $raw =~ s/(\s+)\s*=\s*(\S+)/lc($1)/e while ($raw =~ s/(\s
++)\s*=\s*(\S+)/);
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Updated to say it won't work - the loop will never terminate:( You'd need to use /c and or\G or something somewhere, but I said I ain't good with regexes!

my %params = lc($raw) =~ ...

It will lowercase everything, however :(