Instead of these:

m[^ ( [^|]+ ) \| ]x and $current{ $1 } = $_ while <CURRENT>;
...
    if( m[^ ( [^|]+ ) \| ]x and exists $current{ $1 } ) {
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you could do:

(my $e=index($_,"|"))>0 and $current{substr($_,0,$e)}=$_ while <CURREN
+T>;
...
    if((my $e=index($_,"|"))>0 and exists $current{substr($_,0,$e)) {
[download]

It's a bit more typing, but depending on the string lengths and quantities involved, it might end up running a little faster (and the extra letters spelling out the function names may help to provide a bit of explanation about what's actually going on).

(I guess the scope of the first temporary "$e" will be wider than necessary, given the absence of curly brackets for that "while" loop, but just a little more typing would fix that as well.)