If you really want to write it that way, I think you'd need to use do {...}, e.g. something like this 

my $s = "a,b=c,e=#f";

sub fn { "fn(@_)" }  # dummy function

my %result = map {
        /=#/ ? do { my @l = split(/=#/,$_,2); ( $l[0], fn($l[1]) ) }
             : /=/ ? split(/=/,$_,2)
                   : ($_,fn($_))
    }
    split(/,/, $s);


use Data::Dumper;

print "$s\n";
print Dumper \%result;

[download]

Output: 

a,b=c,e=#f

$VAR1 = {
          'e' => 'fn(f)',
          'a' => 'fn(a)',
          'b' => 'c'
        };

[download]

In reply to Re: map a list by almut
in thread map a list by evil_otto

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