If your entries are always seperated by whitespace you can
do this:

my $string = qq~HHH9114
EEE8888
LLL4258
PPP8525~;
        
$string =~ s/\s+/|/g;

print "||$string||\n";
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That the \s+ is telling it to replace one or more whitespace
characters (\t\n\r etc.), the g tells it to do all occurances.